Question

From 2009 to 2014 the percent of students placing into Math 101 has increased from 13% to 25%. Meanwhile, the percent of students placing into Math 222 has dropped from 25% to 7% If both placements change at a linear rate, what will the percentage be when the percent of people placing into Math 101 is equal to the percent placing into Math 222?

Answer 1

say 100 total students to make it easy

let y = year - 2009 to make it easy
M101
2009 13
2014 25
s = m y + b
m = (25-13)/5 = 12/5
13 = (12/5) 0 + b so b = 13
s = (12/5)y + 13

M222
2009 25
2014 7
s = (-18/5)y + 25

so when is
(12/5)y + 13 = -18 y/5 + 25 ???

30 y/5 = 12

y = 2
so in 2009 + 2 = 2011
then s = (- 36 / 5) + 25
= (125-36)/5 = 17.8 percent