mike withdrawed money from the bank he spent a fourth of it on gas and has $90 left. how much money did he withdraw?
Let's call the amount of money he withdrawed " m " .
m - ( \(\frac14\) )m = 90 Factor out an m on the left side.
m( 1 - \(\frac14\) ) = 90
m(\(\frac44-\frac14\)) = 90
m(\(\frac34\)) = 90 Multiply both sides of the equation by \(\frac43\)
m = 90 * \(\frac43\)
m = 120
If he spent a 1/4 then he must have 3/4 left
So $90 is 3/4 of the original amount
If you divide that by 3 you will have 1/4 of the original amount so
90 / 3 = $30
$30 is 1/4 of the original amount.
If you multiply that by 4 you will have the orriginal amount.
$30 * 4 = $120