Question

You and your best friend are both on the swim team. You want to beat your friend at the next swim meet so you decide to swim 15 minutes longer than she does one day at practice. Write an equation for the number of minutes you swim, y, when your friend swims x number of minutes. You swim 55 minutes. How many minutes did your friend swim?

Answer 1

y=x+15

Friend swims 40 minutes

Explanation:

We re told that you want to swim 15 minutes longer than your friend. In word problems, longer or more always means addition. This means we will add 15 minutes to your friend's swim time (x) so we can figure out how long you swam (y).

This gives us the equation: y=x+15

Part two:

We know that you swam 55 minutes. This means y=55.

55=y=x+15

55=x+15

Now we want to get x alone, or isolate it. We can do this by subtracting 15 from both sides.

55-15=x+15-15

15-15= 0 and 55-15= 40

40=x

Thus your friend swam 40 minutes

(Remember that whatever you do to one side of the equation, you have to do to the other. If you add 2 to the left hand side, you have to add 2 to the right hand side. If you, like we did above, subtract 15 from the right, you have to subtract 15 from the left too)