Step-by-step explanation:
Equation for plane A's descent:
y = - 2500x + 14000
Equation for plane B's ascent:
y = 4000x + 1000
where y = altitude
x = time in minutes
For the altitude to be the same, we would equate both equations:
y = y
-2500x + 14000 = 4000x + 1000
14000 - 1000 -2500x = 4000
13000 = 4000x + 2500x
13000 = 6500x
x = 13000/6500
x = 2
Plotting the graphs: