Question 1: If there are African elephants X and Asian elephants Y, then:

X+Y= 13

6X+3.6Y=66

The second mention: the time for a dog to run is the same as the time for two people to meet, so finding the time for two people to meet is the key to solving the problem;

Meeting time =14/(6+4) =14/10 km/h.

So the dog's distance =14/10 *15 =?

The third question: It is easier to answer this question with indirect unknowns, so suppose it takes my brother x minutes, then:

70x=80x-2* 1*80

Call manually! Hope to adopt! thank you