Question

Given the point (5,6) and the slope of 5, find y when x=21

Answer 1

`\sf{Slope =(y_2-y_1)/(x_2-x_1)}\\\\5 = (y - 6)/(21-5) \\\\5=(y-6)/(16)\\\\16(5) = y-6\\\\80 = y-6\\\\y = 80 + 6\\\\\boxed{\bf{y=86}}`

Answer 2

If slope is 5, 5.(x-5)=y-6 so 5x-y-19=0. When x=21, y=86.