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.
Well! See ,If the endpoints are (x1,y1) & (x2,y2) then mid-point is given by (x1+x2)/2,
(y1+y2)/2
Here in this question endpoints given for the line segment are (-4,2) , (2,4) so we have to find mid-point for x and y co-ordinates by applying above rule.
So, the mid-point we get is (-4+2)/2 , (2+4)/2.
i.e. (-1,3) which lies in 2nd Co-ordinate!
Hope it helps!!
Answer: he washed 18 windows
Step-by-step explanation: count by 10