What should come in place of the question mark '?' in the following question?

$13\times \mathrm{3 }\text{of}\mathrm{ 5}÷26=?+2.5$

The correct option is 5 (Option 4).

To solve the given equation, we follow the standard order of mathematical operations (BODMAS / PEMDAS rule: Brackets, Orders/Of, Division, Multiplication, Addition, Subtraction).

The given equation is:

$13\times 3\text{of}5÷26=?+2.5$

Step 1: Perform the 'of' operation first, which represents multiplication with higher priority than regular multiplication or division.

$3\text{of}5=3\times 5=15$

Substituting this back into the equation:

$13\times 15÷26=?+2.5$

Step 2: Perform the division and multiplication from left to right. Rewrite the division as a fraction:

$\frac{13\times 15}{26}=?+2.5$

Step 3: Simplify the left-hand side by dividing 13 and 26 by their common factor, 13:

$\frac{15}{2}=?+2.5$

Convert $\frac{15}{2}$ to a decimal:

$7.5=?+2.5$

Step 4: Solve for the question mark ('?') by subtracting 2.5 from 7.5:

$?=7.5-2.5$

$?=5$

Therefore, the value that should come in place of the question mark is 5.