7(x - 4) + 28y(x - 4) factor completely if possible,

you can take x - 4 out but I think its prime. Very confusing.

Look for common factors to take out of the two terms.

The obvious being 7 and (x - 4).

If you divide both terms by 7(x - 4), you're left with (1 + 4y) in parentheses.

Therefore this equals 7(x - 4)(1 + 4y)

– Algebra House