I have a problem with this SAT question

So I'm playing around with SAT questions and I stumble upon this.

After about an hour of trying I can't seem to get it right:

Question: http://s3.postimage.org/wel17i1cj/bugproblem.png

So I read the explanation which infuriated me (or perhaps made me feel very stupid, we'll see).

Am I right when I say that they are asking you to solve for ? They then go on to say that which is all fine and dandy but then the function would read: right? Which makes no sense.

It's like saying: '' , where f is the number of units sold and x is the price'', which makes no sense what so ever since denotes a function (same as in their example).

I'm really confused and a little sleep deprived so bear with me...

Re: I have a problem with this SAT question

They ask you to solve for s(20) and by s = 100, they mean s(p)=100 since s is **a function not a variable **, so they say when p = 10, s=100 or s(10)=100

Re: I have a problem with this SAT question

I really feel like they should state: ''S(P) is the number of units sold''. I've never heard it referred to like that. ''S is the number...''..