https://web2.0calc.com/questions/is-there-a-way-to-do-in-ratio-method
Ethan bought a bag of marbles. After giving 1/5 of his marbles to Jacob and 105 marbles to Adam, he had 1/3 of the marbles left. How many marbles did Ethan buy?
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x - (x/5 + 105) = x/3
x = 225
+80 
