Ineed put you have to round to the nearest tenth percent!

16) 1,200 * .1 = 120. That is 10%.

1,200 - 120 = 1,080. Final price.

18(??) ) 5,700 * .6 = 3,420. That is 60%.

5,700 - 3,420 = 2,280. Final price.

15) I'm not positive what this question is asking because there are no directions showing.  If you are trying to determine what 57 is to 98 as compared to x out of 100 (finding the percentage out of 100):

57/98=x/100
cross multiply
5700= 98x
divide both sides by 98
58.16= x
58.2 rounded= x

***This may not be correct if that is not what the question is asking 

16) sale price= subtract original price times the discount from the original price

sale price= $1200 - ($1200 * 10%)
sale price= $1200 - ($1200 * 0.10)
sale price= $1200 - $120
sale price= $1080 sale price of the bicycle

17) sale price= subtract original price times the discount from the original price

sale price= $5700 - ($5700 * 60%)
sale price= $5700 - ($5700 * 0.60)
sale price= $5700 - $3420
sale price= $2280 sale price of the car

Hope this helps!  :)