Answer:
$87.90
Step-by-step explanation:
Let the amount of money Hashim had be $Y. As such, if he gives his mother $28, he would have $Y - $28 left.
If he had $15.20 less than his sister and his sister had $75.10, then we can say that what he had left $Y - $28 is equivalent to the difference between $75.10 and $15.20.
This is
$Y - $28 = $75.10 - $15.20
Y = $28 + $75.10 - $15.20
= $87.90