The answer B is correct, as this is the floor function. The floor function takes the greatest integer below the number, so that's why B is correct.
Total copies = 160
Cost of each copy= $0.045
Total cost = 160*0.045
= $7.2
So listen to your teacher next time
-5-(15y-1) = 2(7y-16) - y // question
-5-15y+1 = 14y-32-y // distribute
-15y - 4 = 13y - 32 // subtract
-28y = -28 // divide
y = 1