MATH
posted by Anonymous .
Aircraft are landing and taking off on parallel runways at a busy airport. On its approach, one aircraft descends from an altitude of 1200m to an altitude of 500m in 35s. During the same time, a departing aircraft climbs from an altitude of 200 m to an altitudes of 1250m.
A) Write a system of linear equations to model the altitudes of the aircraft
B)When are the aircraft at the same altitude? What is that altitude?
I really don't get how to to this, Please help:(

1200500 = 700
so
x = 1200  (700/35)t
1250  200 = 1050
so
y = 200 +(1050/35) t
when does x equal y ? 
what are effects of latitude on weather and climate?