Update ch07.asciidoc

Fixes 3 typos.

ch07.asciidoc

@@ -339,7 +339,7 @@ Transactions can contain inputs with nSequence values less than 2^31^. Any such
 
 The nSequence value is specified in either blocks or seconds, but in a slightly different format than we saw used in nLocktime. A type-flag is used to differentiate between values counting blocks and values counting time in seconds. The type flag is set in the 23rd least significant bit (ie. value 1<<22). If the type-flag is set, then the nSequence value is interpreted as a multiple of 512 seconds. If the type-flag is not set, the nSequence value is interpreted as a number of blocks.
 
-When interpreting nSequence as a relative timelock, only the 16 least significant bits are considered. Once the flags (bits 32 and 23) are evaluted, the nSequence value is usually "masked" with a 16-bit mask (eg. nSequence & 0x0000FFFF).
+When interpreting nSequence as a relative timelock, only the 16 least significant bits are considered. Once the flags (bits 32 and 23) are evaluated, the nSequence value is usually "masked" with a 16-bit mask (eg. nSequence & 0x0000FFFF).
 
 The following diagram shows the binary layout of the nSequence value, as defined by BIP-68:
 
@@ -388,7 +388,7 @@ BIP-113 Median time-past as endpoint for lock-time calculations:: https://github
 
 Fee-sniping is a theoretical attack scenario, where miners attempting to rewrite past blocks, "snipe" higher-fee transactions from future blocks to maximize their profitability.
 
-For example, let's say the highest block in existence is block  #100,000. If instead of attempting to mine block #100,001 to extend the chain, some miners are attempting to re-mine  #100,000. These miners can choose to include any valid transaction (that hasn't been mined yet) in their candidate block  #100,000. They don't have to re-mine the block with the same transactions. In fact, they have the incentive to select the most profitable (highest fee per kB) transactions to include in their block. They can include any transactions that were in the "old" block  #100,000, as well as any transactions from the current mempool. Eseentially they have the option to pull transactions from the "present", into the rewritten "past" when they re-create block  #100,000.
+For example, let's say the highest block in existence is block  #100,000. If instead of attempting to mine block #100,001 to extend the chain, some miners are attempting to re-mine  #100,000. These miners can choose to include any valid transaction (that hasn't been mined yet) in their candidate block  #100,000. They don't have to re-mine the block with the same transactions. In fact, they have the incentive to select the most profitable (highest fee per kB) transactions to include in their block. They can include any transactions that were in the "old" block  #100,000, as well as any transactions from the current mempool. Essentially they have the option to pull transactions from the "present", into the rewritten "past" when they re-create block  #100,000.
 
 Today, this attack is not very lucrative, because block reward is much higher than total fees per block. But at some point in the future, transaction fees will be the majority of the reward (or even the entirety of the reward). At that time, this scenario becomes inevitable.
 
@@ -493,7 +493,7 @@ ELSE
 ENDIF
 ----
 
-Looking at this redeem script, you may be wondering: "Where is the condition? There is nothing preceeding the +IF+ clause!"
+Looking at this redeem script, you may be wondering: "Where is the condition? There is nothing preceding the +IF+ clause!"
 
 The condition is not part of the redeem script. Instead, the condition will be offered in the unlocking script, allowing Alice and Bob to "choose" which execution path they want.