Question

What is 8x + -13x I just want to see if the answers are as quick as it says it is

Answer 1

The answer is -5x. Since your adding like terms it's just subtraction because they are different value integers, one is negative and one is positive. When two opposite integers(+ and -) are being added it is just taking away from the negative what the positive value is. If the positive is greater than it may turn the answer into a positive. Example: 12+-2= 10<-- changed

Answer 2

- 5x. 
In case you actually want to know how I got it:
the question is just saying "8x - 13x".
8 - 13 = -5