Solve using rational equations:
james, kelly, hector, and kyla are painting a house. james could paint the house in 9 hours, kelly could paint it in 7 hours, hector could paint it in 6 hours, and kyla could paint it in 10 hours. how long will it take them to paint it together?

option a is correct.

step-by-step explanation:

scale factor: it is used to find proportional measurements.

proportions means having the same ratio.

scale factor is the ratio of the model measurement to the actual measurement in a simplest form.

or we can say that the ratio of any two corresponding lengths in two similar geometric figures

if the scale factor is more than 1, then it is an enlargement,

if the scale factor less than 1, then it is a reduction.

given the two geometric figure:

by definition of proportions, we have