So the original price is "x".
the discounted price by 10% is P(x) = 0.9x.
the price minus a $150 coupon is C(x) = x - 150.
so, if you go to the store, the item is discounted by 10%, so you're really only getting out of your pocket 90% of that, or 0.9x, but!!! wait a minute!! you have a $150 coupon, and you can use that for the purchase, so you're really only getting out of your pocket 0.9x - 150, namely the discounted by 10% and then the saving from the coupon.
C( P(x) ) = P(x) - 150
C( P(x) ) = 0.9x - 150
To know which fraction is greater than another is to first look at the denominator
<u>example</u>

if u look at the denominator the one with the highest denominator is the smallest and then you look at the numerator to imagine if its closer to the denominator or farther away from the denominator.
I got this answer, I think it’s correct though.
30 students could of been taking both courses and 60 with no course
(x+17)(x+17)=
I believe this is what you are looking for friend