Input: There is a 40% decrease in the input value of 15000 to the output value of 9000. To calculate this percentage change, we can use the following formula:

Percentage change = (New value - Old value) / Old value x 100%

In this case, the new value is 9000 and the old value is 15000. So, we can plug these values into the formula:

Percentage change = (9000 - 15000) / 15000 x 100%

Percentage change = -6000 / 15000 x 100%

Percentage change = -0.4 x 100%

Percentage change = -40%

Therefore, we can conclude that there is a 40% decrease in the input value of 15000 to the output value of 9000. This means that the output value is 40% less than the input value. To reverse this percentage change and find the original input value, we can use the following formula:

Original value = New value / (1 - Percentage change)

Plugging in the values, we get:

Original value = 9000 / (1 - (-0.4))

Original value = 9000 / 1.4

Original value = 6428.57

Therefore, the original input value was 15000 and it decreased by 40% to reach the output value of 9000.