Form an equation and solve it

Question

Hone helps out with fundraising for a local charity by selling chocolates at a stall in a shopping mall. The charity has to pay $120 per day as rent to the owners of the shopping mall. Hone is paid three twentieths of what is left.

On one particular day, Hone was paid $75. Form an equation and solve it to find the total amount of money raised (before the owners of the shopping mall and Hone were paid).

Answer 1

Let T = the total raised

First you have to subtract 120 from the total, then multiply it by 3/20 to get Hone's pay, which we are given. Here's the equation:

(T-120)* (3/20) = 75

Divide both sides by 3/20 (remembering keep-change-flip from pre-algebra, to do fraction division:

75 / (3/20) = 75 * (20/3) = 25 * 20 = 500

so

T-120 = 500

Add 120 to both sides

T = $620