(r+5)×7-54=(r+5)×4помогите :-)

Question

(r+5)×7-54=(r+5)×4
помогите :-)

Answer 1

(r + 5) * 7 - 54 = (r + 5) * 4
7r + 35 - 54 = 4r + 20
7r - 19 = 4r + 20
7r - 4r = 20 + 19
3r = 39
r = 39 : 3
r = 13
(13 +5) * 7 - 54 = (13 + 5) * 4
126 - 54 = 72
72 = 72