Solve for r aarbrSolutiona ar b r To solve for r we need to

Solve for r: a+ar=b+r

a+ ar = b +r

To solve for r, we need to rewrite the equation with r isolated on the left side:

First group terms with r o the left side:

==> ar - r = b -a

Now factor r:

==> r(a-1) = (b-a)

Now divide by a-1 to free r:

==> r = (b-a)/(a-1)