The perimeter of a rectangular land is 100 meters. If the length increases by 13 and the width increases by 14, then the perimeter increases by 30 meters. What is the original area of this land?

The perimeter of a rectangular land is 100 meters. If the length increases by 13 and the width increases by 14, then the perimeter increases by 30 meters. What is the original area of this land?

It is assumed that the length is the same as the length increased by width. 50 × 13-3 △ 2, = 1623-15, = 123 (m), the original width is: 123 △ 13-14, = 53 △ 112, = 53 × 12, = 20 (m), the original length is: 50-20 = 30 (m), the original area is: 30 × 20 = 6

According to statistics, the global desertification land area has reached 36 million square kilometers, accounting for 14% of the total land area, and it is still expanding at a rate of about 60000 square kilometers every year. If we do not stop it, how many years later, there will be no grass on the earth?

(3600 ／ 14-3600) ／ 6, = 10800 ／ 6, = 1800 (year); a: after 1800, not a single grass can be seen on the earth

A piece of land covers an area of 3600 square meters to build school buildings, of which teaching buildings account for 2 / 3, playground 1 / 5 and greening 1 / 9. How many square meters do you calculate?
emergency

Teaching building 3600 * 2 / 3 = 2400 square meters
Playground 3600 * 1 / 5 = 720 square meters
Greening 3600 * 1 / 9 = 400 square meters