6 songs
The way to find this answer is to divide 18 by 3, which is six, which means that after every six songs a commercial is played.
Hope this was helpful and that I explained it correctly.
Answer
1/2 and -4/3
Step-by-step explanation:
N=d-2
q=n+d =>q=(d-2)=q=2d-2
25q+5n+10d=525
replace q and n with d
25(2d-2) +5(d-2)+10d=525
50d-50+5d-10+10d=525
65d=585
d=9
n=7
q=16