Answer:
3+d=q and 0.10d+0.25q=1.80
There are 3 dimes and 6 quarters.
Step-by-step explanation:
This situation has two unknowns - the total number of dimes and the total number of quarters. Because we have two unknowns, we will write a system of equations with two equations using the two unknowns.
We know there are three more quarters than dimes. We write that as 3+d=q.
We also know the total cost and the value of each coin. We write 0.10d+0.25q=1.80.
We substitute 3+d for q in the second equation.
0.10d+0.25(3+d)=1.80
0.10d+0.75+0.25d=1.80
0.35d+0.75=1.80
We isolate the variable by subtracting 0.75 across the equal sign and then dividing by the coefficient of d.
0.35d=1.05
d=3
There are 3 dimes.
