125 = 40 + 15w
W = number of weeks
6 weeks is 125 = 40 + 15(16)
15(16) is 90 so 90 + 40 = 130
So the inequality would be w >= 6
To be more precise because 6 weeks is $130 and not $125, divide 85 (money still needed) by 15 to get the decimal 5.66…, so it would be w >= 5.66…