2x=3- 1

2x=2

x= 1

Substitute x= 1.

Then 1+3a=7.

3a=6

a=2

Substitute a=2.

You can find the value of x.

2、

There are x ships.

(x- 1)9=(x+ 1)6

9x-9=6x+6

9x-6x=6+9

3x= 15

x=5

(5- 1)x9=36 (name)

There are 36 students.

Suppose the speed of the plane is x km/h. ..

5 hours and 30 minutes =5.5 hours

(x+24)5.5=(x-24)6

5.5x+ 132=6x- 144

0.5x=276

x=552

(552-24) X6 = 3168km

A: The distance between the two cities is 3 168 km.

Let Xiao Ming's average speed in the first half hour be X km/h. ..

30 minutes =0.5 hours

0.5x+(0.5x2)x=30

0.5x+x=30

1.5x=30

x=20

A: Xiaoming's average speed in the first half hour is 20 kilometers per hour.

There seems to be a mistake in your second question. Please call me again. If you don't understand, please ask.