Respuesta :

Let B = the weight of box B

Let 2B = the weight of box A

Let 2B + 30 = the weight of box C

B + 2B + 2B + 30 = 640

5B = 610

B = 122 pounds, weight of box B

2B = 2(122) = 244 pounds, weight of box A

2B + 30 = 2(122) + 30 = 274 pounds, weight of box C

hope this helps

Answer: 90b (grams)

Step-by-step explanation:

Given statement : A box weighs 90 grams.

Let b denotes the number of boxes, then the weight of b boxes will be :-

[tex]\text{Total weight of b boxes}=b\times\text{Weight of one box}\\\\\Rightarrow\ \text{Total weight of b boxes}=b\times90\\\\\Rightarrow\ \text{Total weight of b boxes}=90b[/tex]

Hence, the expression for the weight  ( in grams) of b boxes : 90b