If the sequence of the alphabets is reversed, which of the following would be the $13\text{th}$ letter from your left?

The standard alphabetical series consists of $26$ letters: $A=1,B=2,\dots ,Z=26$.
When the entire sequence is completely reversed, it begins from $Z$:

$$1:\text{Z},2:\text{Y},3:\text{X},4:\text{W},5:\text{V},6:\text{U},7:\text{T},8:\text{S},9:\text{R},10:\text{Q},11:\text{P},12:\text{O},13:\text{N}$$

Mathematically, the $n\text{th}$ position from the left in a reversed sequence corresponds to the position $(27-n)$ in the standard sequence:

$$27-13=14$$

The $14\text{th}$ letter of the standard alphabet is N.