To arrive at a shared binomial in Step 3, Kevin should modify how he groups the terms in Step 2. The ideal approach is to use different factors for -7x in Step 1.
Step 1 should be adjusted to use factors that align well for grouping. For instance, instead of -3x and -4x, if he uses -2x and -5x, he can set up the grouping in such a way that both parts will yield a common factor.
So, the correct change is:
Use different factors for −7x in Step 1.
This way, when he completes the grouping, he will be able to create a shared binomial in Step 3.