Question

Jan is saving money to buy a bike. The bike costs $255. She has $120 saved and each week she adds $15 to her savings. Write and solve an equation to find how long will it take her to save enough money to buy the bike.

Answer 1

Answer is 9 weeks

Step by step

We can use the y intercept formula
y = mx + b

The cost of the bike is “y” $255
The starting point is “b” $120 saved
The rate is “m” $15 per week
Our unknown amount of weeks is x

$255 = $15x + $120

Solve for x

Subtract 120 from both sides to isolate x

255 - 120 = 15x + 120 - 120

135 = 15x

Divide both sides by 15 to solve for x

135 /15 = 15/15 x

9 = x

9 = amount of weeks

We can check our work by substituting 9 in place of x in our equation

255 = (15)(9) + 120

255 = 135 + 120

255 = 255