If L stands for +, M stands for -, N stands for x, P stands for ÷, then 6 N 8…

To solve this expression, we must first substitute the given letters with their corresponding mathematical operations and then apply the correct order of operations (BODMAS/PEMDAS).

Step-by-Step Analysis
Define the Substitutions:

L = +

M = -

N = ×

P = ÷

Substitute into the Expression:

Original: 6 N 8 L 21 P 3 M 4

Substituted: 6 × 8 + 21 ÷ 3 - 4

Apply Order of Operations (BODMAS):

Division: 21 ÷ 3 = 7. The expression becomes 6 × 8 + 7 - 4.

Multiplication: 6 × 8 = 48. The expression becomes 48 + 7 - 4.

Addition: 48 + 7 = 55. The expression becomes 55 - 4.

Subtraction: 55 - 4 = 51.