solve in terms of r:s=a/1-r

To solve the equation in terms of r, we'll need to isolate r on one side of the equation.

s = a/(1 - r)

To get rid of the fraction, we can multiply both sides of the equation by (1 - r):

s * (1 - r) = a

Next, distribute s to both terms in the parentheses:

s - s * r = a

Rearranging the equation by bringing -s * r to the left side:

-s * r = a - s

Now, we can isolate r by dividing through by -s:

r = (a - s) / -s

However, we can simplify this equation by dividing both numerator and denominator by -1:

r = (s - a) / s

So, the equation in terms of r is r = (s - a) / s.