Question

The sum of three numbers is 21. Three times the smallest is 3 less than the largest, while the sum of the largest and smallest is 15. Use linear system in three variable to find the three numbers

Answer 1

One of the numbers is 6.
The other is 12.
The last is 3.

Difficult, but not impossible!

Answer 2

3, 6, 12
I guessed and checked. So if 3 is the smallest number, I would, multiply it by 3, which is 9. 9 is 3 less than the largest number which would be 12. 12 + 3 is 15. To find the third number, subtract 21 and 15 which is 6