Step 1: Analyse Question StemWe have to find out a unique value for the expression x + y.
Therefore, we should be able to manipulate expressions to obtain x + y OR we should be able to find the individual values of x and y, and then add them to obtain x + y.
Step 2: Analyse Statements Independently (And eliminate options) – AD / BCEStatement 1: x + y + z = x + y – z + 1
Transferring all variable terms to the LHS, we have,
x + y + z – x – y + z = 1
Simplifying, z = ½.
Knowing the value of z is not sufficient to find out x, y or x + y.
The data in statement 1 is insufficient to find out a unique value of the given expression.
Statement 1 alone is insufficient. Answer options A and D can be eliminated.
Statement 2: x – y + z = 0
Knowing that the value of the expression equals Zero, is not sufficient to find out x, y or x + y.
The data in statement 2 is insufficient to find out a unique value of the given expression.
Statement 2 alone is insufficient. Answer option B can be eliminated.
Step 3: Analyse Statements by combiningFrom statement 1: z = ½
From statement 2: x – y + z = 0
Combining both, we can say that x – y = - \(\frac{1}{2}\)
Knowing the value of x – y is not sufficient to find x, y or x + y, since infinite combinations of x and y can satisfy this equation.
The combination of statements is insufficient to find out a unique value of the given expression.
Statements 1 and 2 together are insufficient. Answer option C can be eliminated.
The correct answer option is E.