Answer: 10
Explanation:
I’m not sure where the N fits into the equation, but if you are finding the amount that w holds, 10 is correct.
Reverse the equation: 20=15+.5w
Now move .5 over and do 20-15 which equals 5.
.5w=5
5 divided by .5 gives you the answer of 10. 10•.5=5 which means 10 is your answer!