Company A: y = 50x + 15
Company B: y = 130x + 55
Set the equations equal to each other and solve for x (number of weeks).
50x + 15 = 130x + 55
Subtract 50x from both sides:
15 = 80x + 55
Subtract 55 from both sides:
-40 = 80x
Did you have a typo? The companies will never have the same cost because company B costs so much more and weeks cannot be negative.