The operation is defined for all integers a and b by the equation ab = (a - 1)(b - 1). If y12 = 110, what is the value of y ? Choose the correct option
A) 11  B) 12  C) 13  D) 15  E) 18

Rationale: ab = ( a - 1 ) ( b - 1 ) y 12 = ( y - 1 ) ( 12 - 1 ) = 110 - - > y - 1 = 10 - - > y = 11 answer : a
Answer: A