The first step is to find the values of x and y. From the information given,
x is the cost of an adult ticket and y is the cost of a child ticket. The system of equations is shown below
3x + 5y = 50
x + 5y = 31
From the second equation,
x = 31 - 5y
We would substitute x = 31 - 5y into 3x + 5y = 50. We have
3(31 - 5y) + 5y = 50
By expanding the parentheses, we have
93 - 15y + 5y = 50
- 15y + 5y = 50 - 93
- 10y = - 43
Dividing both sides of the equation by - 10,
- 10y/- 10 = - 43/- 10
y = 4.3
Substituting y = 4.3 into x = 31 - 5y, we have
x = 31 - 5 * 4.3 = 31 - 21.5
x = 9.5
If an adult ticket costs $9.5, then the cost of 4 adult tickets is
4 x 9.5 = $38