p = h - 11
53p + 45h = 784.10
just a matter of subbing and solving...
53(h - 11) + 45h = 784.10
53h - 583 + 45h = 784.10
98h = 784.10 + 583
98h = 1367.10
h = 1367.10/98
h = 13.95
p = h - 11
p = 13.95 - 11
p = 2.95
so paperbacks (p) are 2.95 a piece and hardbacks (h) are 13.95 a piece