Question

Factor 14a - 7b.
7b(2a)
7(b - 2a)
7(2a - b)

Answer 1

what would you like to be factored?

Answer 2

look here this a tutorial:
7b(2a)=6b times 2a = 14ab and this is not the answer

the second one 7(b-2a)= 7 times b -7 times 2a = 7b-14a and this not what we want so the last one is true

Answer 3

and by the way, the second step is incorrect, as is the third.
If you wanted to show as many steps as possible, then your work should look like this:

14a - 7b <-------find GCF
(7)(2)(a) - (7)(1)(b) <------- notice both have a (7) in common
(7)( (2)(a) - (1)(b) ) <-------simplify terms
7(2a - b)

however this is not needed, it is just as easy to do
14a - 7b
(7)2a - (7)b
7(2a - b)

or
14a - 7b
7(2a - b)

Answer 4

Oh they are answer choices... then the last is the answer choice.