Answer:
Matt has 7/12 of the jar of marbles left.
Step-by-step explanation:
In order to find this, simply subtract the 3/4 from the full jar (1) and then add 1/3. They will need common denominators to complete this operation.
1 - 3/4 + 1/3 = Amount
12/12 - 9/12 + 4/12 = Amount
7/12 = Amount