Well if the student already finished 6 problems out of 15, there are 15-6 = 9 homework questions she still has to finish.
Still needs to complete: 9.
Already finished: 6
9 : 6.
Simplified: 3 : 2
1: 8 faces and 9 with the base 9 vertices and 16 edges
2: 3 faces and 5 with the bases 6 vertices and 9 edges
3: 3 faces and 4 with the base 4 vertices and 6 edges
Hope this can help you.
The answer is 12. 3/4 and 1/16 have a common denominator of 16. multiply 3/4 by 4 and get 12/16. divide that by 1/16 and get 12/1 making the answer 12.
Depending on what you need help with I am here at any time :/