Respuesta :

choixongdong
 (x + 9) + (3x + 7)
= 4x + 16

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Combine the x terms since they are like terms and combine the constant terms since they are like terms. 

x + 3x = 4x
9 + 7 = 16
4x + 16 

Hopefully this helps and let me know if you need more help!