Answer:
They will cross the finish line together in 175 minutes.
Explanation:
This question asks you to consider the 25 and 35 times table. 
I listed the 25 and 35 times tables and tried to find the lowest common multiple. 
You can see that on Josephs' 7th lap of the track he will cross the line simulatneously with Owuor who will be on his 5th lap. So the answer should be 175 minutes. 
25 × 1 = 25 35 × 1 = 35
25 × 2 = 50 35 × 2 = 70 
25 × 3 = 75 35 × 3 = 105 
25 × 4 = 100 35 × 4 = 140 
25 × 5 = 125 35 × 5 = 175 
25 × 6 = 150 35 × 6 = 210 
25 × 7 = 175
25 × 8 = 200