Ok, let's see what we got here, q=1/2p+15, solve for p, here's the steps:
q=1/2p+15
-15 -15
q-15=1/2p
*2 *2
2q-30=p, or you can write it as p=2q-30
*I multiplied two at the last step because 2 is the reciprocal of 1/2, it just gonna make it more confusing if you divide it by 1/2, so the best solution here is to multiplies 1/2 by it reciprocal, which is 2.
