A = 10 months
B = First part, the two equations:
Ian: y = 1000 - 60x, where x is the number of months and y is the remaining balance owed.
Ken: y = 600 - 20x.
They will be equal at 1000 - 60x = 600 - 20x
Second part: Solve the equation. Note, if you're equation is incorrect, solve it anyway because you will still get some credit!
1000 - 60x = 600 - 20x
1000 = 600 + 40x
400 = 40x
x = 10 months
y = 600 - 20(10) = 600 - 200 = $400 still owed.
C =
Solve Ian's equation for y = 0, when no money is owed.
1000 - 60x = 0
1000 = 60x
x = 16.66666.... or 17 months.
Ian will not be paid off 6 months after he and Ken owe the same amount. He will still owe money.
Alternatively, six months after 10 is 16 months,
and y = 1000 - 60(16) = 1000 - 960 = 40. He will still owe $40 at 16 months, so he is not paid off.