If the letters of the words 'RANGE' and 'MUSCLE' are grouped together and arranged in ascending English alphabetical order, which letter will be the $3^{\text{rd}}$ letter to the left of the $4^{\text{th}}$ letter from the right?

Let's gather all letters from the words 'RANGE' and 'MUSCLE':
$$\text{Letters: }\text{R, A, N, G, E, M, U, S, C, L, E}$$

Now, arrange them in English alphabetical order:

$$\text{Sorted: }\text{A, C, E, E, G, L, M, N, R, S, U}$$

Total number of letters = $11$.

We need to find the $3^{\text{rd}}$ letter to the left of the $4^{\text{th}}$ letter from the right.

$$\text{Target Position from the Right}=4+3=7^{\text{th}}\text{ letter from the right}$$

Let's count the $7^{\text{th}}$ letter from the right side of the sorted sequence:

* $1^{\text{st}}$ from right = $\text{U}$
* $2^{\text{nd}}$ from right = $\text{S}$
* $3^{\text{rd}}$ from right = $\text{R}$
* $4^{\text{th}}$ from right = $\text{N}$
* $5^{\text{th}}$ from right = $\text{M}$
* $6^{\text{th}}$ from right = $\text{L}$
* $7^{\text{th}}$ from right = $\text{G}$

Alternatively, from the left end: $\text{Position}=11-7+1=5^{\text{th}}\text{ letter from the left}$.
Looking at the sorted list, the $5^{\text{th}}$ letter from the left is $\text{G}$.