Alex ran 12.8 km in the morning. After lunch, he continued running. When he finished the run, he had covered 31.4 km in all. Write an equation that can be used to find how far Alex ran after lunch.

Let r be the distance in kilometres that Alex ran after lunch.

12.8 km + r = 31.4 km

Step-by-step explanation:

First, Alex ran 12.8 km, then he ran an r amount of km. Added together they equal 31.4 km.

If you need to solve the equation you subtract 12.8 from 31.4 and will give you the amount of miles he ran after lunch.

Ex.: r = 31.4 km - 12.8 km

r = 18.6 km

Alex ran 18.6 km after lunch