Solution:
Let the number of adult tickets be

Let the number of children tickets be

The total number of tickets bought is

Therefore,
The equation to represent the number of tickets will be

The cost of one adult ticket is

The cost of children's tickets is

The cost of x number of adult tickets will be

The cost of y number of children tickets will be

The total amount spent on the tickets is

Therefore,
The equation to represent the total amount of money spent will be

Combine the two equations together and then solve simultaneously

Step 1:
Using the elimination method, make x the subject of the formula from equation (1) to form equation (3)

Step 2:
Substitute equation (3) in equation (2) to get the value of y

Step 3:
Substitute y=6 in equation (3) to get the value of x

Hence,
The number of adult tickets jake bought = 3