Any value of m makes the equation true.
All Real Numbers
Use PEMDAS
P Parentheses first
E Exponents (ie Powers and Square Roots, etc.)
MD Multiplication and Division (left-to-right)
AS Addition and Subtraction (left-to-right)

A is the right option! Because 0.40 should be in second equation with the x to represent the number of stamps multiply by 40 cents.
Answer:
$375
Step-by-step explanation:
3750 × 10%
3750 × 10/100
375