Answer:

Where P represent the kilograms of pears for this case and if we solve for P we got:

And we can check that the total sum is 8.7:

So then the final answer would be 3.48 Kg of pears
Explanation:
For this case we know that the total amount sold was 8.7 Kg. And we know in addition that 3/5 of this weight is from apples. So then the rest
correspong to pears.
We can set up the following equation:

Where P represent the kilograms of pears for this case and if we solve for P we got:

And we can check that the total sum is 8.7:

So then the final answer would be 3.48 Kg of pears