The sum of three numbers is 3. if the second number is subtracted from the sum of the first and third numbers, the result is 9. if the third number is subtracted from the sum of the first and second numbers, the result is -5. find the three numbers.

Let the three numbers be x, y, and z.

If the sum of the three numbers is 3, then x+y+z=3

If subtracting the second number from the sum of the first and third numbers gives 9, then x+z-y=9

If subtracting the third number from the sum of the first and second numbers gives -5, then x+y-z=-5

This forms the system of equations:
[1] x+y+z=3
[2] x-y+z=9
[3] x+y-z=-5

First, to find y, let's take do [1]-[2]:
x+y+z=3
-x+y-z=-9
2y=-6
y=-3

Then, to find z, let's do [1]-[3]:
x+y+z=3
-x+-y+z=5
2z=8
z=4

Now that you have y and z, plug them into [1] to find x:
x+y+z=3
x-3+4=3
x=2

So the three numbers are 2,-3, and 4.

Are you asking for 6 or 15?