The concentration of chlorine in the atmosphere serves as an indicator of damage to the ozone layer. The table to the right shows relationships of chlorine concentration in parts per billion to the year​

Let's say that the cost of a ticket in japan is $x and the cost of a ticket in switzerland is $y:

(1) 3x + 2y = 81.51
if we multiply both sides of the equation by 2 we get: 6x + 4y = 163.02
(2) 3y + 2x = 77.39
if we multiply both sides of the equation by 3 we get: 9y + 6x = 232.17

now let's subtract equation (1) from equation (2):
9y + 6x - (6x + 4y) = 232.17 - 163.02
5y = 69.15
y = 13.83

substituting this into (the original) equation (1) we get:
3x + 2(13.83) = 81.51
3x + 27.66 = 81.51
3x = 53.85
x = 17.95

thus the average cost of a ticket in japan is $17.95 and then average cost of a ticket in switzerland is $13.83