Answer:
There are 18 dimes in the jar
Explanation:
Let
x = number of dimes in the jar
y = number of quarters in the jar
Total = $3.80
There are ten less quarters than dimes
y = x - 10
0.1x + 0.25y = 3.80
0.1x + 0.25(x - 10) = 3.80
0.1x + 0.25x - 2.5 = 3.80
0.35x = 3.80 + 2.5
0.35x = 6.30
x = 6.30/0.35
x = 18