I think they will meet in 4 minutes.
Explanation
10+15+15+15+15=70
150-20-20-20-20=70
Every minute the first balloon goes up 15 meters and the second balloon goes down 20 meters.
Answer:
The correct answer is D. The points are rotated 180 degrees and scaled by a factor of 0.5. I assume that the 0.5 is the expected value in the text box labelled "D" (for dilation perhaps?)