Question

Trip has 15 couns worth 95 cents. Four of the coins are worth twice as much as the rest. Construct a math argument to justify the conjecture that Trip has 11 nickels and 4 dimes.

Answer 1

n+d=15
5n+10d=95

n=-d+15
-5d+75+10d=95
5d=20
d=4
n=11

The equations n+d=15 and 5n+10d=95 prove that he has 4 dimes and 11 nickels