A2-mi cab ride costs $4.25. a 7-mi cab ride costs $8.50. which equation models the cost y of a cab ride that is x miles?
a. y= -0.85x+2.55
b. y= 0.85x-2.55
c. y= 0.85x+2.55
d. y= -0.85x-2.55

The number of volunteers to walk dogs at the local animal shelter last year was 20. this year, the number of volunteers has risen to 50. what is the percent of increase in the number of volunteers?