If you turn one of the numbers in each pair backwards, and then merge it with the regular number, you'll get the mentioned shape. For example, 3 (backwards) + 3 (normal) gives you an 8 shape. 7 (backwards) + 7 (normal) gives you a triangle. And the same with the 2.
It is if you put the numbers together you get the answer. 3 + 3 = 8.
i.e one number forwards one number backwards.
RT = ....