Respuesta :

first do the equations in the parentheses 

(21)+(28) the first one isn't negative anymore because a negative times a negative is a positive. 
Now we just add them, 21+28=49
-3x -7 + 4x + 7

= 4x - 3x - 7 + 7

= x - 7 + 7

= x

Or.. if your are doing it this way then it would be

(-3 * -7) + (4 +7)

= 3 * 7 + 4 +7

= 21 + 4 + 7

= 32

Hope these help! :)