Your friend sells "for"adult tickets and 15 student tickets for $27, I think you meant "four" adult tickets and 15 student tickets for $27.
Answer:Adult ticket costs $3
Student ticket cost $1
Explanation:
Let the cost adult ticket be represented as X
And cost student tickets be represented as y
Such that two adult tickets and six student tickets for $12 would be expressed as
2x+6y=12
And
four adult tickets and 15 student tickets for $27.
4x+15y=27
The equations to solve becomes
2x+6y=12-----equation 1
4x+15y=27------equation2
Solving
Multiply equation 1by 4 and equation 2by 2
8x+24y=48---equation 3
8x+30y=54-----equation4
Subtracting equation 3from equation 4
6y=6
Y=6/6
Y=1
Putting the value of y=1in equation 1and solving for x becomes
2x+6y=12
2x+6x1=12
2x=12-6
2x=6
X=6/2=3
Adult ticket costs $3
Student ticket cost $1