The advertisement shows the price of tickets to enter an amusement park. Mr Lee went to the amusement park with his wife and 4 children. What is the least amount of money Mr Lee paid for all the tickets?
Cost of 1 adult ticket and 1 child ticket if they are bought separately
= 5 + 3
= $8

Amount saved if 1 adult ticket and 1 child ticket are bought as 1 set instead of separately
= 8 - 6
= $2

Buying tickets by sets of 1 adult ticket and 1 child ticket is cheaper.

2 adults means Mr Lee can get 2 sets of 1 adult ticket and 1 child ticket.

Cost of 2 sets of 1 adult ticket and 1 child ticket
= 2 x 6
= $12 

Number of remaining children to buy for
= 4 - 2
= 2

Cost of child tickets for 2 children
= 2 x 3
= $6

Least amount of money that Mr Lee has to pay for all the tickets
= 12 + 6
= $18

Answer(s): $18