In 25 minutes li can run 10 laps around the track. consider the number of laps she can run per minute

Here you are going from 25 minutes to 1 minute; essentially, if you look at this algebraiclly you have 25 min=10 laps to 10 minutes= x laps; set up a proportion for this to get: 25 min/10 laps =1minutes/ x laps Solving by cross multiplying; multiply the denominator to the opposite numerator (this makes more sense when writing as a fraction; you will multiply in an "x" shape) then solve as the algebra problem of 25=10x ; divide both sides by 10 to isolate x and this will give you the answer of x=2.5