Question

What numbers add up to 3 & multiple to 10

Answer 1

Well, factors of 10 are:
1 and 10
and
2 and 5

Those don't add up to three. However, if it was -10, then 5 and -2 would add up to three.

Answer 2

There are no real numbers that can do that job.

The numbers are

       1.5 + i √7.75
and
       1.5 - i √7.75

These are called 'complex numbers'.  The symbol ' i ' stands for √-1  .

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If either the ' 3 ' or the ' 10 ' was actually supposed to be negative,
then the two numbers would be  2  and  -5 .