All even numbers are divisible by 2 since that's what even means.
We only need two even numbers whose sum is less than 180 because 180 is also even and subtracting the sum from 180 gives us the third number.
To find all such numbers we start with 2 and 4, add them together (=6) and subtract this sum from 180 (=174).
Then we continue with 2 and 6, making 8, 180-8=172; then 2 and 8 and 170; 2+10+168; 2+12+166; and so on; then 4+6+170; 4+8+168; 4+10+166; and so on; then 6+8+166; 6+10+164; and so on and so on.
Eventually we get to 58+60+62 and we've found them all!