Question

sally gave her brother 3.95 in quarters and dimes. if the number of quarters is 6 more then the number of dimes, how many quarters did sally give her brother

Answer 1

Let q be the number of 25 cent coins.
Let d be the number of 10 cent coins.
0.25q+0.10d= 3.95...(1)
q-d=6...(2)

(2)->    q-d= 6
       q-d+d= 6+d
              q= 6+d...(2a)

(2a)-> (1)      0.25q+0.10d=3.95
              0.25(6+d)=0.10d= 3.95
           1.95+0.25d+0.10d= 3.95
                               0.35d= 3.95-1.5
                       0.35d/0.35= 2.45/0.35
                                      d= 7...(3)

(3)->(2)     q-d= 6
                 q-7= 6
                    q=6+7
                    q= 13
There are 13 quarters and 7 dimes.