Find an equation of the line through the points (-1,1) and (1,5)

First of all, to find the slope, you need to subtract the y's in the numerator over the x's in the denominator. Then you use Y-Y₁=slope(X-X₁) using either of the two points. If you want to simplify it further into slope-intercept form, you need to distribute on the right side of the equation.

Aand b are correctly balanced reactions. they have the same number of atoms in both sides of the reaction