1 penny is just 1c
one nickel is 5 pennies or 5c
alrite...
p = amount of pennies in the jar
n = amount of nickels in the jar
we know there are 56 coins in the jar, thus whatever "p" and "n" are,
p + n = 56
we also know, the total value of all pennies and nickels is one buck and 52 cents, or 1.52.. that's 152 pennies.
now, we know there are 5 pennies in one nickel, so in "n" nickels, there are 5*n pennies, or 5n, thus
p + 5n = 152

solve for "p", to see how many penny coins are there.
what about the nickels? well, n = 56 - p.