I need some help with writing expressions?...?

Question

it's actually pretty simple but i forgot how...

1) How much is a 15% tip on a restaurant bill of x dollars?

2) You have $15 and buy r raffle tickets for $0.50 each. How much money do you have left?

1) is it something like.... 15/100= ?/x

2)?

Answer 1

You have the correct equation for 1.  Generally 15/100 is written as the decimal .15.  Since you want to solve for ? the answer is .15x because you multiply both sides of the equation by x.  So the tip is .15x read as "point fifteen times x."

For the second question a single raffle ticket costs .5, or fifty cents.  Then r raffle tickets cost .5r or point five times r.  Since you want to know how much money is left, you have to subtract this from the amount you started with.  Then you have 15 - .5r dollars left.

Hope this helps you!