Answer:
We'll let x represent the number of weeks it will take to save enough money. If she saves $11 each week, then in x weeks she will save 11x dollars.
Add this to the 107 she has already saved, and at the end of 11 weeks she will have 11x + 107 dollars.
We want the amount saved to be equal to the price of the bike, so our equation is
11x + 107 = 173
In a word problem, writing the equation is usually the hardest part. Now we solve the equation.
Subtract 107 from both sides to get
11x = 66
Divide both sides by 11 to get
x = 6 weeks.
