Question

A coin container has 10 more nickels than dimes and together the nickels and dimes are worth $3.50. How any nickels and dimes are in the container?

Answer 1

let n be the number of nickels and d the number of dimes
n = d + 10 by looking at the first sentence
0.1d + 0.05n = 3.50 since nickels are 5c ea and dimes 10c a piece.
Do you like elimination or substitution better?

Answer 2

Hitchhiking on bluepig's work:

n = d + 10
0.1d + 0.05n = 3.50 --> Multiply by 100 -> 10d + 5 n = 350

n = d + 10
10d + 5n = 350

10d + 5 (d+10) = 350
10d + 5d + 50 = 350
15d + 50 = 350
15d = 300
d = 20 ---> 20 dimes

n = d + 10
n = 20 + 10 = 30 ---> nickels