If you want to factor -2 out of -6x + 10, simply divide everything by -2 and put the result in a parentheses times -2:
(-6x + 10)/-2 = 3x - 5
Therefore, the factored form would be -2(3x - 5).
If you want to check the answer, just redistribute the -2:
-2 * 3x = -6x and -2 * -5 = 10
-6x + 10 <----- It checks out
Hope this helps! :)