I'm embarrassed to admit I failed, it is actually tricky

I'm embarrassed to admit I failed, it is actually tricky...

Find the correct result.

Please just post the answer not how you work it out otherwise it gives it away and what's the point in other people trying.

(I will send you confirmation either way.)

1+4=5

2+5=12

3+6=21

5+8=_________

If your answer is wrong, upload it in your timeline.

GAME?

Originally posted on Facebook on April 04, 2020.