Let the number be 10x + y.∴ x + y = 12 ...........(i)10x + y - (10x + x) = 18or 10x + y - 10y - x = 18or 9x - 9y = 18∴ x - y = 2From (i) and (ii), x = 7, y = 5∴ Number = 75
Suppose the digit at unit's places is y and that at ten's places is x.Then, the number = 10x + y,According to the question.x + y = 8 .......(i)Again 10x + y - 18= 10y + x= 10x + y - 10y - x = 18= x - y = 2 ............(iii)From, equation (i) and (iii) we get x + y = 8x - y = 22x = 10= x = 5 and y = 3∴ number = 10 x 5 + 3 = 53