Question 1179863

 
Let Mary = a
Let Mark = b
Let w = number of weeks
 
We know that: a=20+15w
b=20+20w
 
In 6 weeks, just plug in w=6.
 
A = 20 + 15*6 = 110
B = 20 + 20*6 = 140
 
Mary: 110 dollars
Mark: 140 dollars