#### Answer

The point of intersection is (4,48) which means that an order of 4 tickets will have the same total cost when ordering online or at the door.

#### Work Step by Step

(a)
Ordering online, the cost is 10dollar × t + 8dollar a service charge.
The equation for online order is
c=10t+8
Buying at the door will cost 12dollar × t
The equation for Buying at the door is
c=12t
The System of equation is
c=10t+8
c=12t
(b)
The Graph will be: