maths

[Apple33]

What is the easy way to answer the following questions?

Here are two ways of making a total of 12 from three different whole numbers:
2+3+7=12. 3+4+5=12

A) Write down all the ways of making a total of 12 using three different whole numbers (don't count 2+3+7 as different from 2+7+3)

B) how may ways are there of making a total of 15 using three different whole numbers

[Guest55]

I 'd start by thinking about two numbers that add to 12

1 + 11

now split the 11 into two numbers 1 + 2 + 9, 1 + 3 + 8, 1 + 4 + 7, 1+ 5 + 6 others are duplicates or repeat ( 1 + 1 \+ 10)

then repeat