The drama club is selling tickets to their play to raise money for the show's expenses. Each student ticket sells for $5.50 and each adult ticket sells for $9.50. There was a total of $703 in revenue from the sale of 98 total tickets. Write a system of equations that could be used to determine the number of student tickets sold and the number of adult tickets sold. Define the variables that you use to write the system.

Let's define the variables:

Let's call the number of student tickets sold as 's'
Let's call the number of adult tickets sold as 'a'

Now we can write the system of equations:
1. The total number of tickets sold is 98:
s + a = 98

2. The revenue from student tickets is $5.50 per ticket and the revenue from adult tickets is $9.50 per ticket. We know that the total revenue was $703:
5.50s + 9.50a = 703

Therefore, the system of equations is:
s + a = 98
5.50s + 9.50a = 703