math
posted by Ruby .
A family spends 20% of its monthly income on food, 23% on rent, and 42% on other expenses and saves the balance. If the family saves $360 per month, what is its monthly income?

Think of it as 20% of what is 360.
Percent over 100 and is over of.
So, 20/100 = 360/x
360 x 100 = 36000
Divide this by 20 and you will have your answer.