The final amount of money was $50, they spent half of what they collected on canned foods, so 50 x 2 = 100.
They collected a total of $100.
Let the amount Eric collected = X
Charlotte collected 3 times as much minus $20, writing this as an equation you get 3x-20.
Now you have Eric plus Charlotte = $100:
x + 3x-20 = 100
Combine like terms:
4x-20 = 100
Add 20 to both sides:
4x = 120
Divide both sides by 4:
x = 120/4
x = 30
Eric = X = $30
Charlotte = 3x-20 = 3(30) - 20 = 90 -20 = $70
