Answer:
x = 7 (the number of students)
Step-by-step explanation:
let students = x , adults =y
Equation 1: the total number of them
x+y=25 (25 because there are 5 for free)
Equation 2: the total price of them
2x+5y=104 (student cost 2$, adult cost 5$)
so we have two equations
x+y=25 (by multiply this equation by -2)
so it will be -2x-2y=-50
by adding 2 equations
-2x-2y=-50
2x+5y=104
0+3y = 54 divide both side by 3
y=18 (the number of adults)
by sub. in Equation (x+y=25)
x+18=25
x=25-18
x = 7 (the number of students)