Random maths tip

For example: You're given a point (3,1) and u need to find out what a is in (7,a) The gradient is 2 right?

Easy trick, just go up by 2 in the y axis then. (3,1) (4,3) (5,5) (6,7) (7,9)

(7, a) = (7, 9)

Check Desmos if u wanna check

Whatever formula and stuff they teach aren't as good as this (I think)