Find the volume of the first box which is l*w*h and second box which is also l*w*h and add them. (6*4*5) + (10*10*2)
Divide 25.7 by 141.

Now, multiply that with 100 percent to get the percentage.

18.22% is your answer! If the question wants you to round it to the nearest percent, the answer will be 18%.
No, Perry is not using the correct ratio, because 15:17 is not equivalent to 5:7
15 divided by 3 is indeed 5 but divided 17 by 3 does not give you 7, nor a whole number.
I hope this helps.