Answer:
Option a :   
 
Step-by-step explanation:
 Given : 
The drama club sold 100 tickets to a show, it had $300 in profit.
The next show, it had sold a total of 200 tickets and had a total of $700 profit.
To Find :  Equation models the total profit, y, based on the number of tickets sold, x
Solution :
For 100 tickets he had $300 in profit .
⇒ ( )=(100,300)
)=(100,300)
For 200 tickets he had $700 in profit .
⇒ ( )=(200,700)
)=(200,700)
We will use point slope form i.e. 
 --(A)
 --(A)
Now, to calculate m we will use slope formula : 



Now, putting values in (A)
  
 
Thus Option a is correct i.e. 