Question

Marco owed his father $250 and began paying him back $20 at the end of each week, beginning November 1st. Joni owed her father $150 and began paying back $10 at the end of each week, beginning on the same day. What Marco owed his father in dollars at the end if n weeks can be represented by f(n) = 250 - 20n. What Joni owed her father in dollars at the end of n weeks can be represented by g(n) = 150 - 10n.

Answer 1

The important clue here is when they say both The girls owe the same amount so what they mean is equate both the functions

so we get

150 - 20n = 130 - 15n


Now n gives us the number of weeks so solve for n

20n - 15n = 150 - 130

5n = 20

n = 4

Now check your solution

150-20(4) = 70

130 - 15(4) = 70

So our answer checks out after 4 weeks both girls who their dads the same amount of money .