Answer:
The answer is r = -20/7
Step-by-step explanation:
20 + 8r = -4r + 5 r⇒ collect like term
20 + 8r = r⇒separate different terms in different sides
20 = r - 8r
20 = -7r⇒divide both sides by -7
r = 20/-7
r = -20/7
