Let the hamburgers be x and cheese burgers be y.
x + y = 24
3x + 3.5 y = 79
x = 24 - y.
Substituting the value of x,
3( 24 - y) + 3.5 y = 79
72- 3y + 3.5 y = 79
72 + 0.5 y = 79
0.5y = 79 - 72 = 7
1/2 y = 7
thus, y = 7 * 2 = 14
Substituting the value for x,
x + y = 24
x + 14 = 24
x = 24-14 = 10
Thus, x = 10.
Thus, she sold 10 hamburgers and 14 cheeseburgers
