Question

How many coins are dimes?

Answer 1

The correct answer is D or 26 cents

Having 3 less dimes than pennies denotes having 6 pennies or 6 cents, then 3 dimes is equal to having 15 cents. 6+16=26

Answer 2

p+d=9

p=9-d  we are also told that: 

d=p-3

p=d+3....since p=p we can say

d+3=9-d  add d to both sides

2d+3=9  subtract 3 from both sides

2d=6  divide both sides by 2

d=3, and since p+d=9, p=9-d so

p=6

So Jack has 3 dimes and 6 pennies which is:

3(0.10)+6(0.01)

0.30+0.06

$0.36

So he has 36 cents.