Question

put the number 1 to 9 in the box belong so that each side of the triangle adds up to 20​

Answer 1

Answer:

In a 3x3 grid, I'd have to put numbers from 1 to 9 in a manner so that respective row, column and diagonal add up to 15.

I have only been able to come up with one solution:

672159834

Through some calculations and trial and error method.

Is there any strategy or way of approach to this problem, or is trial and error method the solution to it?