Let x be the number of dimes and let y be the number of quarters:

Then ................................(1)

since he has the amount in dollars, try to write x and y in terms of dollars:

so,

....................(2)

(2) can be simplified as:

....................(3)

Note that the denominators in the above equation(2) denotes the number of coins that make a dollar. 10 dimes = $1 and 4 quarters = $1

Now can you solve equations (1) and (3) for the values of x and y???

you will have

19 dimes

9 quarters