Answer:
Carrie and Joan have 80 nickels and 40 dimes, respectively, and each one has an amount of money of 4 US dollars.
Step-by-step explanation:
Let be
and
the amounts of nickels and dimes that Carrie and Joan have, as
the total amount of money that both Carrie and Joan have. A nickel is a five cent coin and a dime is a ten cent coin.
The following equations are constructed after a careful reading on statement:
Carrie's amount of money:
(Eq. 1)
Joan's amount of money:
(Eq. 2)
Relation between amounts of coins:
(Eq. 3)
First we eliminate
by equalizing (Eq. 1) and (Eq. 2):

Then, we reduce the resulting formula by (Eq. 3):



And rest of variable are now determined:




Carrie and Joan have 80 nickels and 40 dimes, respectively, and each one has an amount of money of 4 US dollars.