Answer:
Excuse me if this is wrong but I think you have to multiply 3 x 2.4 which is 7.2 and that is greater that 3.0.
Step-by-step explanation:
Add all 3 and you get 264 then divide by 3 and you get 88
258 cubic inches
Since the boxes are kind of on their own—>
First box: 7*2*12 = 168
Second box: 5*2*9=90
168+90 = 258