I don't know what 5 step process your teacher or book advocates, but when working word problems translate the words into math. This problem defines two situations, so define and write each as math.
Call the number of copies x.
Copy Cats charges a flat fee of $21 plus $.15 per page for a batch of color prints. That's 21 + .15x.
Heritage charges a flat fee of $25.50 plus .12 per page. That's 25.5 + .12x.
The problem asks to identify when Heritage is cheaper, or less than, Copy Cats. So it's 25.5 + .12x < 21 + .15x. Solve for x. Subtract 21 from both sides and .12x from both sides.
4.5 < .03x | Divide both sides by .03.
150 < x
Hope the solution helped. Sometimes you need more than a solution. Contact fcabanski@hotmail.com for online, private tutoring, or personalized problem solving (quick for groups of problems.)