Update prompts-advanced-usage.md

Fix the minor content error mentioned in issue #49

guides/prompts-advanced-usage.md

@@ -403,7 +403,7 @@ The first step involves a large language model (as an inference model) that is g
 
 APE discovers a better zero-shot CoT prompt than the human engineered "Let's think step by step" prompt (Kojima et al., 2022).
 
-The prompt "Let's work this out it a step by step to be sure we have the right answer." elicits chain-of-though reasoning and improves performance on the MultiArith and GSM8K benchmarks:
+The prompt "Let's work this out in a step by step way to be sure we have the right answer." elicits chain-of-though reasoning and improves performance on the MultiArith and GSM8K benchmarks:
 
 ![](../img/ape-zero-shot-cot.png)