Answer:the length of time he spent running is 8 minutes.
the length of time he spent swimming is 15 minutes.
Step-by-step explanation:
Let x represent the length of time he spent running.
Let y represent the length of time he spent swimming.
He exercised for a total of 23 minutes. This means that
x + y = 23
When running he burns 35 calories per minute, and when he swims he burns 30 calories per minute. He has burned 730 calories after exercising. It means that
35x + 30y = 730 - - - - - - - - - -1
Substituting x = 23 - y into equation 1, it becomes
35(23 - y) + 30y = 730
805 - 35y + 30y = 730
- 35y + 30y = 730 - 805
- 5y = - 75
y = - 75/ -5
y = 15
Substituting y = 15 into x = 23 - y, it becomes
x = 23 - 15 = 8
