Explanation:
and ... ? what do we need to do ?
I guess finding the number of quarters and dimes.
x = number of quarters
y = number of dimes
x + y = 185
x = 185 - y
0.25×x + 0.1×y = 26.75
after all, a quarter has a value of $0.25, and a dime of $0.10.
let's use the identity of the first equation in the second equation :
0.25×(185 - y) + 0.1×y = 26.75
to make is simpler to see let's multiply the whole thing by 100 :
25×(185 - y) + 10y = 2675
4625 - 25y + 10y = 2675
4625 - 15y = 2675
1950 = 15y
y = 130
x = 185 - y = 185 - 130 = 55
there are 55 quarters and 130 dimes in the bag.