make a the subject of p = (3a+5)/(4-a)

so step 1) remove the denominator by multiplying (4-a) by p. Therefore obtaining p(4-a) = 3a+5. step 2) multiply out to get 4p-ap = 3a+5 step 3) have all the a's on one side, and non a's on other side. therefore: 4p-5 = 3a+ap step 4) factor out the a's. 4p-5 = a(3+p) step 5) make a = (4p-5)/(3+p)