(1) The land area of the earth is about1.500 million kilometers, which is 2 1 100 million square kilometers less than the ocean area. How many billion square kilometers is the ocean on the surface of the earth?

Solution: Suppose the ocean on the earth's surface is X billion square kilometers.

Equation: X- 1.5 = 2. 1.

X=3.6

A: The ocean on the earth's surface is 360 million square kilometers.

(2) The park received 365 visitors in the morning, 5 more than 1.2 times in the afternoon. How many tourists did the park receive in the afternoon?

Solution: The park received X tourists in the afternoon.

Equation: 1.2x+5=365.

x=300

The park received 300 visitors in the afternoon.

The number of science and technology books in the library is three times that of comic books. There are 392 fewer comic books than science books. How many science books and comic books are there?

Solution: There are X science books and Y comic books.

Equation: X=3y

X-y=392

y= 196

x=588

Answer: 588 science books and comic books 196.