Given:
Bobby put 1/3 of his lawn mowing money into his savings
He uses the remaining 2/5 to buy a video game.
He has $12 left.
To find:
The amount did he have at first.
Solution:
Let x be the initial amount.
Bobby put 1/3 of his lawn mowing money into his savings. So, the remaining amount is
He uses the remaining 2/5 to buy a video game. Then the remaining amount is
It is given that the remaining amount is $12.
Divide both sides by 2.
Therefore, Bobby have $30 at first.