After an airplane reached its cruising altitude, it climbed for 10 min. Then it descended for 15 min ...

Using a substitution Strategy to solve a system of Linear Equations After an airplane reached its cruising altitude, it climbed for 10 min. Then it descended for 15 min. Its current altitude was then 1000 m below its cruising altitude. The difference between the rate of climb and the rate of descent was 400 m/min. What were the rate of climb and the rate of descent?