You may want to review adding and subtracting positive fractions first.

To add signed numbers, first you check if the two numbers have
the same sign or opposite signs. If they have the *same*
sign, then their sum also has that sign, and you can add their
values to get the value of the sum. For example, −4 +
(−3) = −7. If they have *different* signs, then
the sign of the answer is the sign of whichever one is bigger. So
5 + (−4) will be positive, but 5 + (−7) will be
negative. (Note that by “bigger” here we just mean
that the value is bigger, ignoring the sign.) The value of the
answer will be the *difference* of the two values. So 5 +
(−4) = 1 and 5 + (−7) = −2.

To subtract signed numbers, just flip the sign of the second one and then add them. So 7 − 10 = 7 + (−10), which is −3, but 7 − (−10) = 7 + 10, which is 17.