Which of the following are factors of x^2+5x-6?
(A.) (x+2) (x-3)
(B.) (x-2) (x-3)
(C.) (x+6) (x-1)
(D.) (x+2) (x+2)

I chose C I just want to know if i'm doing this right.

C is correct

to double check your answer, just multiply both terms together.

as a quick and dirty tip to help narrow it down, you know the constant term is -6, so you can just multiply the constant terms together to narrow it down for you. A => -6, B => 6, C => -6, D => 4. so you know it's either A or C. multiply them both out to see which is right.

Another way to answer this question easily is observing three little things:

1) look if the number near x^2 is 1.
you have 1.x^2 + 5.x - 6
ok

2) now all you have to is to sum numbers of each answer till you find the result 5
(a) +2 -3 = -1
(b) -2 -3 = -5
(c) +6 -1 = +5
(d) +2 +2 = +4

3) now you have to check the product of the numbers. If you get a result equal -6, you found your answer.
Look on letter (a). You have product equal -6, but the sum is not +5.

so letter C is the answer.

Try this one:
x^2 +5x +6

you will see the answer is (x+2).(x+3)