Two families go to a theatre. the smith family three adults and four children pays £67. the jones family five adults and six children pays £106.work out the price of an adult and child ticket, let a stand for adults and c stand for child

1.)    5 (3a + 4c = 67)  
2.)    -3 (5a + 6c = 106)

1.)    15a + 20c = 335
2.)    -15a - 18c = -318

                     2c = 17
divide both sides by 2
c = £8.5
substitute c for 8.5 to find a

3a + 4 * 8.5 = 67
3a + 34 = 67
subtract 34 from both sides
3a = 33
divide both sides by 3
a = £11

Ican't do any of the other stuff, but i can get you started. the answer, i believe, is $2.50.