It's supposed to be (0,-3) but I guess your answer should be A
First we need to multiply to make the fractions have equal denominators so we can add/subtract.
math: 1/3 x 4/4=4/12
science: 1/4 x 3/3=3/12
Now we can find the time she spent on history (I assume this is what you are looking for)
Total time-math time<span>-science time=history time</span>
12/12-4/12-3/12
=5/12
Amy spent 5/12 of her time working on history.
The answer is 110 because if you multiply 8•16=128 and 18 cars are used, you subtract 128-18 which is 110.