Enjoy the fruits of mankind.

1 saves 220 million sheets of paper a day, which is 22,000,000/220,000 =1000 tons.

1000/0.69= 1449.3 tons of wood,

1449.3×3.44=4985.5 cubic meters of wood

Let x minutes later, the distance between them and the school be equal.

2000-90x= 1500-65x

The solution is X=20.