.
Sierra has fifteen fewer pennies than quarters. Sierra has a total of 25 pennies and quarters. How much money does she have?
~~~~~~~~~~~~~~~~~~~~~~~~
1. "Sierra has fifteen fewer pennies than quarters." ====> P = Q - 15
where P = the number of pennies, and Q = the number of quarters.
2. "Sierra has a total of 25 pennies and quarters." ====> P + Q = 25.
You have two equations:
P = Q - 15, (1) and
P + Q = 25. (2)
From (1), substitute the expression P = Q-15 into (2), replacing P. You will get
(Q-15) + Q = 25.
Simplify and solve
2Q - 15 = 25,
2Q = 25 + 15,
2Q = 40 ====> Q = = 20.
The number of quarters is 20.
Hence, the number of pennies is 25-20 = 5.
Answer. 5 pennies and 20 quarters.