A = number of tickets sold to adults
C = number of tickets sold to children
Set up the system of linear equations based on the scenario.
2.75A + 2.25C = 279.25
A + C = 109
Use the substitution method: C = 109 - A
2.75A + 2.25(109 - A) = 279.25
2.75A + 245.25 - 2.25A = 279.25
0.5A + 245.25 = 279.25
0.5A = 34
A = 68
Plug in 68 for A to find C.
68 + C = 109 → C = 41
2.75(68) + 2.25(41) = 187 + 92.25 = 279.25
68 adults and 41 children went to the concert.