Answer:

1.   L = 175 – 10w and M = 200 – 15w, where

L = the amount Lynda owes,

M = the amount Maria owes, and

w = # of weeks.

2.   Maria will pay back her parents first.

·         To find who will pay their parents back first, use 0 as the amount owed and solve for the variable. 

Lynda will pay her parents back the $175 in 18 weeks.

                 0 = 175 – 10(w)

-175 = (-10)w

17.5 = w

Maria will pay her parents back the $200 in 14 weeks.

     0 = 200-15(w)

-200 = (-10)w

13.3 = w

      An alternative:

·         The slope for Maria is –15 and the slope for Lynda is only –10, which means Maria is paying back her parents at a faster rate.  

The y-intercept for Maria is only slightly larger because she owed only $25 more than Lynda. 

Since the slope for Maria’s equation is decreasing at a faster rate, she will pay her parents back first.