Answer
Austin has 41 marbles at the beginning.
Step-by-step explanation
Let the number of marble Austin has be x.
Charles has 3 times as many marbles as Austin has implies 3x
If he gives 75 marbles to Austin, then;
Charles now has 3x - 75
Austin now has x + 75
Charles will be left with 48 marbles implies;
Charles marbles is now 3x - 75 = 48
Therefore, the number of marbles Austin has at the beginning can be calculated as shown below.
3x- 75 = 48
3x = 48 + 75
3x = 123
Divide both sides by 3
(3x/3) = 123/3
x = 41 marbles
Hence, Austin has 41 marbles at the beginning.