We can write equations by rewriting the important phrases of information using variables. These variables make the equation look neater and it is faster to write a letter instead of constantly repeating 'cost of student tickets', for example.
The important pieces of information lies in the second last sentence of this question.
- the tickets of your friend, her mom and her little sister costs a total of $23
- the tickets of 2 adults and 3 students costs a total of $39
Now, let's rewrite them into equations.
Given
x= cost of adult tickets
y= cost of student tickets
Assuming that your friend and her little sister are students, the two equations are:
- x +2y= 23 -----(1)
- 2x +3y= 39 -----(2)
To convert these equations into slope-intercept form, move all the terms that are not y to the right-hand side of the equation before dividing both sides by the coefficient of y. This is to ensure that the coefficient of y is 1 and that your equation is in y= mx +c, where m is the slope and c is the y-intercept.
From equation (1):
x +2y= 23
2y= -x +23
Divide both sides by 2:
From equation (2):
2x +3y= 39
3y= -2x +39
Divide both sides by 3:
The solution to the system of equations is the point at which the two lines intercept on the graph. I have attached the graph as an image.
The solution is (9, 7).
The x coordinate is the cost of an adult ticket, while the y coordinate is the cost of a student ticket. This means that adult tickets cost $9 and student/ child tickets cost $7.