Given the slope and one point, writing y = mx + b comes down to a single unknown: the intercept. These free printable worksheets hand over both m and a point and ask for the whole equation, so the one move to practice is backing out b.
If they get stuck
The answer key prints on a separate page.
The slope is already given, so the work is one signed subtraction: b = y − mx. With m = 2 through (1, 3), that is b = 3 − 2 · 1 = 1, so the line is y = 2x + 1. Where the two-points sheet makes a child find the slope first, this page removes that step to concentrate on the intercept — which is where the sign errors live, since mx is subtracted and a negative point or a negative slope flips it.
It is the gentler of the two writing-linear-equations skills and a good place to start: with the slope in hand, a child sees clearly how a single known point pins the whole line down. Every step-by-step walk here substitutes the point, solves for b, and writes the finished equation, so the answer is never left as a slope alone.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Point-slope equation of a line, step by step