Consider the following sum: • +1• +2• +• 3 + • 1 = 21• In the above sum, • stands for

The sum is a numerical puzzle where '•' represents a single digit. Let '•' be the digit x. The terms in the sum are interpreted as follows: • = x 1• = 10 + x 2• = 20 + x •3 = 10x + 3 •1 = 10x + 1 21• = 210 + x

Substituting these into the sum: x + (10 + x) + (20 + x) + (10x + 3) + (10x + 1) = 210 + x

Combine like terms on the left side: (x + x + x + 10x + 10x) + (10 + 20 + 3 + 1) = 210 + x 23x + 34 = 210 + x

Now, solve for x: Subtract x from both sides: 22x + 34 = 210

Subtract 34 from both sides: 22x = 210 - 34 22x = 176

Divide by 22: x = 176 / 22 x = 8

So, '•' stands for 8.

Let's verify with x = 8: 8 + 18 + 28 + 83 + 81 = 218 8 + 18 = 26 26 + 28 = 54 54 + 83 = 137 137 + 81 = 218

The left side equals 218, and the right side (21•) also equals 218. The solution is consistent.

Comparing with the options: A) 4 B) 5 C) 6 D) 8

The calculated value is 8, which matches option D.

The final answer is D