The walker family and the goodman family ate going to the cinema. the walkers pay £22 for 2 adults tickets and 1 child ticket. the goodmans pay £26 for 1 adult and 3 child tickets.
how much does a child ticket cost?

The walkers pay 22 for 2 adult tickets and one child ticket so we can say:

2a+c=22, The question wants to find the cost of a child ticket so solve this for a...

2a=22-c

a=(22-c)/2

Now we are told that the Goodmans by 26 for one adult and three childrens tickets so:

a+3c=26, now use (22-c)/2 in this equation for a and you get:

(22-c)/2+3c=26

(22-c+6c)/2=26

22+5c=52

5c=30

c=6

So a child's ticket costs £6.00