Solution: 70%X-60%X=30

10%X=30

X=300

Substitute X=300, and A is 70%, which is already 30%.

70%X=2 10

30X=90

A: It turns out that Team A has 2 10 people and 90 people.

2. Answer: The speed ratio of Party A and Party B is 3:4, and the speed ratio of Party B and Party C is 2:3 (Party B and Party C are multiplied by 2 at the same time to get 4: 6). Then the speed ratio of A, B and C is 3: 4: 6. The ratio of a to c is 1: 2.

The speed ratio of propylene to butadiene is 4:9. (A and C are multiplied by 2 at the same time to get 2: 4). The speed ratio of methyl, propyl and butyl is 2: 4: 9.

Therefore, the speed ratio of butadiene is 2: 9.

3. Solution: (100 *14/25-50 *12/25) * 3/8.

=(56-24)*3/8

=32*3/8

= 12

Answer: Boys in Class Two 12.