Suppose: it takes x minutes to go uphill and y minutes to go downhill (x+y= 16 because going to school 16 minutes is divided into uphill and downhill, X+Y= 16 because it takes x minutes to go uphill and y minutes to go downhill).

X+Y= 16

4800 * X/60+ 12000 * Y/60 = 1880

Solution: X= 1 1.

Y=5

It took 1 1 minute to go uphill and 5 minutes to go downhill, making a total of 16 minutes.

Suppose there are x pigeons on the tree and y pigeons under the tree.

Then all pigeons are (x+y)

(y- 1)/(x+y)= 1/3①

x- 1=y+ 1②

② Simplify to get x=y+2.

Substitute x=y+2 into ①.

The solution is y=5.

∴x=7

There are 7 pigeons in the tree and 5 pigeons under the tree.