65- 15=50 yuan

50÷ 10=5 digits

A: They went to five parents.

(3) 10×2+30×5= 170 yuan.

8×2+30×4= 136 yuan

170 yuan > 136 yuan

A: There are two kinds. It is most cost-effective to buy group tickets.

Page 72

One,

1, 450009307 450009305 million

2、0 4

3、80

4、 1/3 0.3 1 0.3 3.3%

5、200

6、9 8 10

7、3. 14 6.28

8、 1/2:0.4= 1/4:0.2

Second,

Right, wrong, right, wrong

Third, bb bb C.

I don't know if it is ....