Air balloon #1 is 10 meters above the ground rising 15 meters per minute. air balloon #2 is 150 meters about the ground descending 20 meters per minute in how many minutes will the balloons be at the same height

 Remember that Distance = Speed x Time

When the 2 Balloons meet, they will be at the same height FROM THE GROUND :

Distance travelled by #1 : 10 + 15.Time
Distance travelled by #2 : 150 - 20.Time (the descending speed is negative)
Since it's the same distance from the ground, we can write:

10 + 15.Time =150 -20.Time 
15.Time + 20.Time = 150 - 10
35.Time = 140

And Time = 4 minutes

Now take any equation and plug in Time = 4:

10 + 15.Time = 10+15x4 = 70 meters

OR

150 - 20.Time = 150-20x4 = 70 meters

First subtract 10 from both side
y^2+6y-16=0
(y+8)(y-2)=0
-8 and 2