Question

how do you rewrite 7bx+7by

Answer 1

Set 7b as a common factor and put it outside the parentheses:
7b(x+y)

Check:
7b(x+y)
Distribute the 7b
7bx+7by

Hope this helps. 

Answer 2

first you have to find the common factors of the two,

there are two 7 on both sides. so 7 is a common factor.

there are two bs on both sides, so b is also a common factor.

there is only one x in it, so x is not a common factor.

there is only one y in it, so y is not a common factor.

so the common factors are 7 and b.
so 7b should be on the left side of the brackets,

7b(?)

inside should be the numbers or algebra which wasn't an common factor, so it should be (x+y)

if we put this together it will be,
7b(x+y)

answer= 7b(x+y)