Answer:
42.57
Step-by-step explanation:
10+39+71+39+76+38+25=298
298/7=42.57
Ryan's marbles = x
Marie has 4 times less marbles then Ryan would have if he lost 15 marbles (it means he would have x-15)
So, Marie marbles = (x-15):4
If Ryan lost 75 marbles (it means he would have x-75), he would have 1 1/2 times as many marbles as Marie.
We got an equation:
Multiply both sides by 8:

Add 600 and subtract 3x on both sides:

Divide both sides by 5:

Answer: Ryan have 111 marbles.