Answer:
3x+5y=105
x+y=25
Explanation:
x is the number of 3 mile runs so the total distance travelled is 3x miles. y is the number of 5 mile runs so the total distance travelled is 5y miles. Together Gavin travelled 103 miles so 3x+5y=105.
The number of 3 mile and 5 mile runs he did in total were 25 so x+y=25.
So the answer is:
3x+5y=105
x+y=25
Done.