misterJJ2u wrote:

From a list of 1-8, how many ways can you pick 3 numbers so that the sum of the numbers is 12?

Having answer choices might help.

x + y + z = 12

x=1 then y+z = 11. So 3 combinations here.

x=2 then y+z = 10. So 2 combinations here.

x=3 then y+z = 9. So 3 combinations here. (exclude 6+3)

x=4 then y+z = 8. So 3 combinations here.

x=5 then y+z = 7. So 2 combinations here. (exclude 5+2)

x=6 then y+z = 6. So 2 combinations here.

x=7 then y+z = 5. So 2 combinations here.

x=8 then y+z = 4. So 1 combination here.

So total combinations = 18.

I see no patterns in this problem.