the points (2,r) and (6,-7) lie on a line with slope -2 find the missing coordinate r

Question

i need help please 

Answer 1

(r - (-7)) / (2 - 6) = -2        combine

(r + 7) / -4 = -2                 multiply both sides by -4

r + 7 = 8                           subtract 7 from both sides

r = 1