Hi Sara,
Let's see what we have here.
8 friends bought tickets to a hockey game @$x
4 of them also bought a guide book @ $6
If y = total cost
y = 8x + 4(6) 8 people bought tickets and 4 bought guides
y = 8x + 24
You can also write this as
y = 4(x+6) + 4x 4 people bought tickets and guides and 4 people bought only tickets
Distributing and combining terms
y = 4x+24+4x
y = 8x + 24