Respuesta :

Simple....

you have:  4(x+7)

To simplify it..distribute..

4(x+7)

4*x=4x
and
4*7=28

Leaving you with...

4x+28

As we can see B is 4x+28

Thus, your answer.
4x+28 is the right answer because you would use the distributive property which makes  4(x+7)------> 4x+28