Answer or Solution :
This is just an analytical puzzle than a mathematical puzzle.
Logic: Invert the first number horizontally and not vertically, so that it becomes the mirror image of the number.
Now join the inverted mirror image with the 2nd number.
(Mirror Image)2+2 looks like a fish drawing.
(Mirror Image)3+3 looks like number 8.
(Mirror Image)7+7 looks like a triangle.