Answer:
a = c/(d - r)
Step-by-step explanation:
Multiply both sides by a
(c/a)a = (d - r)*a Notice how this is written. You need to introduce brackets on the right because both d and r are multiplied by a.
c = (d - r)*a
Divide both sides by (d - r)
c/(d - r) = a*(d - r)/(d - r)
c/(d - r) = a
