What is the solution of p+15=a and 5a-525=2p

You have a system of equations going on here. The first one is already set equal to a. So let's take that part of the equation, the p + 15, and sub it in for the a in the other equation: 5 (p + 15) - 525 = 2p. Now what we have is an equation to solve that is only in terms of p, not p and a. We cannot solve an equation with 2 unknowns. Making that substitution eliminates the a, the second unknown. Now distribute the 5 into the parenthesis to get 5p + 75 - 525 = 2p. Move the 2p over to the left and move the other terms over to the right and combine all the like terms to get 3p = 450. Dividing both sides by 3 gives you that p = 150. Now take that p value and sub it into the p + 15 = a to get 150 + 15 = a and a = 165

P + 15 = a

5a - 525 = 2p

The first equation is already set equal to a, so plug it into the second equation for a.

5 (p + 15) - 525 = 2p

Distribute.

5p + 75 - 525 = 2p

Combine like terms.

5p - 450 = 2p

Subtract 5p from both sides.

- 450 = - 3p

Divide both sides by - 3

150 = p

p + 15 = a

150 + 15 = a

165 = a

a = 165, p = 150