Answer:
Insert quotation marks after it.
Step-by-step explanation:
When using quotation marks with dialogue, you use quotation marks before the dialogue and after, for example:
"The quick fox jumped over the lazy brown dog."
The sentence 'I'm going to do it.' only had one quotation mark, and that was before it. It was missing the second one. Correctly, it would be "I'm going to do it."