We have a jar of coins, all pennies and quarters. All together, we have 214 coins, and the total value of all coins in the jar is $ 23.98. How many pennies are there in the jar?
Let's assume the number of pennies is x.
The number of quarters is 214 - x.
The value of pennies is x * $0.01 = $0.01x
The value of quarters is (214 - x) * $0.25 = $0.25(214 - x)
The total value of all coins is $23.98
$0.01x + $0.25(214 - x) = $23.98
$0.01x + $0.25 * 214 - $0.25x = $23.98
$0.01x + $53.50 - $0.25x = $23.98
-$0.24x = $23.98 - $53.50
-$0.24x = -$29.52
x = -$29.52 / -$0.24
x = 123
There are 123 pennies in the jar. Answer: \boxed{123}.