Question

The points (-3, 12) and (-1, r) lie on a line with slope - 3. Find the missing coordinate r.

Answer 1

r = 6

Explanation:

(12-r) / ((-3-(-1)) = -3/1

`(12-r)/(-2)` = -3

cross-multiply:

12 - r = 6

subtract 12 from each side:

-r = -6

divide each side by -1:

r = 6