answer: the maximum number of weeks Sally can remove $50 from the account and still have at least $75 is 11 weeks.
show my work :
Let W be the number of weeks Sally has been withdrawing money. The total in the account would be represented by 650-50W at any given time.
To remain over or equal to $75 the equation to solve is
650 - 50W >= 75
we need to get the variable on one side and the constants on the other so subtract 650 from each side...
-50W >= 75-650
-50W >= -575
Now we need to divide out the coefficient of the variable so divide both sides by -50. Note that multiplying or dividing an inequality by a negative reverses the inequality so...
W <= (-575)/(-50)
W <= 11.5
So in whole numbers the maximum number of weeks Sally can remove $50 from the account and still have at least $75 is 11 weeks.