Question

(-15,4) and (r,10) lie on a line with slope 1/2 find the missing coordinate r

Answer 1

Apply the slope formula

$m=\frac{y2-y1}{x2-x1}$

where:

m = slope = 1/2

(x1,y1) = (-15,4)

(x2,y2)= (r,10)

replacing:

$\frac{1}{2}=\frac{10-4}{r-(-15)}$

Solve for r

Cross multiply:

1 (r+15) = 6 (2)

r+ 15 = 12

r= 12-15

r= -3