1. Solution: Let these three numbers be x, 3x. And seven times.

x+3x+7x= 144

Solution: x= 144/ 1 1.

So these three numbers are: 144/ 1 1, 532/ 1 1,1008/1.

2. solution: the solutions of these two numbers are x and y respectively.

According to the meaning of the question

y/3-x=4

4x=y

Solution: x= 12, y=48.

3. Solution: Let the ages of Party A and Party B be X and Y respectively.

According to the meaning of the question

x-y= 15

(x-5)/2=y

Solution: x=25, y= 10.

So, B is ten years old.