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 that the number of pennies in the jar is x.
Therefore, the number of quarters in the jar will be 214 - x.
The value of x pennies is x cents.
The value of (214 - x) quarters is (214 - x) * 25 cents.
The total value of all the coins in the jar is x + (214 - x) * 25 cents.
We can write this as an equation: x + (214 - x) * 25 = 2398.
Multiplying 25 by 214 - x gives us 5350 - 25x, so the equation becomes x + 5350 - 25x = 2398.
Combining like terms, we get 5350 - 24x = 2398.
Subtracting 5350 from both sides, we get -24x = -2952.
Dividing both sides by -24, we get x = 123.
Therefore, there are 123 pennies in the jar. Answer: \boxed{123}.