Ed has an equal number of dimes and nickels and no pennies A

Ed has an equal number of dimes and nickels and no pennies. After spending 15¢, he has twice as many dimes as nickels. How many nickels did he have originally?

Solution

1 dime = 10 cents
1 nickel = 5 cent

Let there be originally x dimes and x nickels
To spend 15 cents, he must spend 1 dime and 1 nickel or 2 nickel
If he spends he must spend 1 dime and 1 nickel
number of dime = x-1
number of nickel = x-1
Both become equal so this is not the case

He must spend 2 nickel
number of dime = x
number of nickel = x-2
From question:
number of dimes = 2*number of nickel
x = 2*(x-2)
x = 2x-4
x = 4
Answer: 4 nickel originally