We can solve this by setting up an equation. I am setting the amount of marbles that tim has as T. Because Sue has twice as many marbles as Tim, she will have 2T marbles. We do not need a variable for Jim, because he has 15 marbles. Now, we can set up this equation:
T + 2T + 15 = 63
Now, we can solve for T. First, we subtract 15 from both sides.
T + 2T = 48
Next, we combine all the T terms.
3T = 48
Finally, we divide both sides to find how many marbles Tim has.
T = 16
So, Tim has 16 marbles.
