Option (a) ⇒ The generalised form of the number is expressed as the sum of the product of its digits with their respective place values x + y is simply the sum of the digits of the number xy Therefore option (a) is incorrect.

Option (b) ⇒ 10x + y = 10 × X + 1 x Y clearly it is the sum of the product of digits with their respective places (Tens and ones). Hence 10x + y is the generalised form of xy.

Option (c) ⇒ 10x – y is the difference of product of digits with their respective places but in generalised form it is the sum. Therefore (c) is incorrect.

Option (d) ⇒ 10y + x = 10 x Y + 1 x X it is the general form of the number yx but question is asking about xy .Therefore (d) is incorrect.