One conveyor belt can move 1000 boxes in 9 minutes. Another can move 1000 boxes in 11 minutes. If another conveyor belt is added and all three are used, the boxes are moved in 3 minutes. How long would it take the third conveyor belt alone to do the same job?

It would take 7.62 minutes for the third conveyor belt alone to do the same job

Step-by-step explanation:

The together rate is the sum of each separate rate.

In this question:

First conveyor: Rate of 1/9.

Second: Rate of 1/11.

Third: Rate of 1/x.

Total: 1/3

So

It would take 7.62 minutes for the third conveyor belt alone to do the same job

x² + 3x + 7 = 0       [ax² + bx + c]

a = 1

b = 3

c = 7

quadratic formula:

    (+/- is this ±)

plug in the numbers into the variables

your answer is a