Answer:

m=60 minutes
Explanation:
Let 'm' be the total number of minutes .
If Spencer usually plans to stop and rest for about 15 minutes.
Then the total time for biking=

Since biking burns about 10 calories per minute.
Total calories burn=

As Spencer wants to burn 450 calories while biking.
It gives the equation
, where m is the total minutes.
To solve this divide both sides by 10, we get
