Here, Let the number of weeks = x
Then, Equation would be: 850x - 300x - 7500 = 0
550x = 7500
x = 7500 / 550
x = 13.63
Minimum week can't be in decimal, so we have to pick for nearest larger value which is 14.
In short, Your Answer would be: 14 Weeks
Hope this helps!