let

a = the number of adults

k = the number of kids

Tickets cost $5.50 each for adults. Tickets cost $3.00 for kids. The total cost was $26.00:

5.50a + 3.00k = 26.00

There were 3 fewer adults than kids:

a = k - 3

by solving the system of equations:

5.50a + 3.00k = 26.00

a = k - 3

we find:

a = 2 adults

k = 5 kids

click here to see the step by step solution of the system of equations:

there were 2 adults and5 kids.