What equation would I use to solve?

Question

An athlete training for a marathon completed a total of 20 miles. If she ran 10 miles more than the distance she walked, for what distance did she run?

Answer 1

When possible, assign a variable to the value being sought.  Here, let x=distance run

 

  Distance run + distance walked = 20 miles

           x         +  ( x -10)            = 20

          2x - 10 =20

           2x = 30

              x = 15    ran 15 miles

 

Answer 2

Let x be running and y be walking 

 

total distance: x+y=20

ran 10 more than she walked: x=y+10

y+10+y=20

2y=10

y=5 miles walking

 

20-5=15 miles running