(xxx)b = x(b2 + b1 + b0)10 x(b2 + b1 + b0)10 = (62)10 x(b2 + b1 + b0)10 = (62)10 x = 2 or 31 But x is a digit. So, it cannot be 31; x must be 2. (b2 + b1 + b0)10 = (31)10 = (52 + 51 + 1)10 = (52 + 51 + 50)10 b = 5 So, (b + x) = (5 + 2) = 7 So, the correct option is (D) : 7.