If '+' means '-', '×' means '+', '÷' means '×', and '-' means '÷', then what…

In symbol-substitution reasoning problems, every operator in the given expression must first be replaced by the operation it is defined to mean, not the symbol that is visually printed. Once every operator has been replaced, the new expression is evaluated using the standard order of operations (BODMAS): all multiplication and division are carried out first, in left-to-right order, and only then is addition and subtraction carried out, again in left-to-right order.

1. The given meanings are: '+' means '-', '×' means '+', '÷' means '×', and '-' means '÷'.

2. Replace every operator in 48 + 6 × 2 - 1 ÷ 4 with its defined meaning: the '+' before 6 becomes '-', the '×' becomes '+', the '-' before 1 becomes '÷', and the '÷' before 4 becomes '×'.

3. The expression becomes 48 - 6 + 2 ÷ 1 × 4.

4. Resolve the division and multiplication first, left to right: 2 ÷ 1 = 2, then 2 × 4 = 8.

5. Resolve the remaining addition and subtraction, left to right: 48 - 6 = 42, then 42 + 8 = 50.

As an independent check, regroup the reduced expression 48 - 6 + 8 by its signed terms: adding the two positive terms first gives 48 + 8 = 56, and then removing the 6 gives 56 - 6 = 50 — the same value, which confirms the arithmetic. Note that the left-to-right rule inside 2 ÷ 1 × 4 is essential and must not be reordered: division and multiplication rank equally in BODMAS, so carrying out the multiplication first would wrongly turn the term into 2 ÷ 4.

Hence, the value of the expression is 50.