Question

Which of the following is not equivalent to x - y + z?

Answer 1

You have to be sure the signs are the same. It doesn't matter the order.
The third choice has x as a negative so it is incorrect.

Answer 2

Y - x + z

A good way to tackle this problem is to check for the signs of all the variables. In your original expression, x-y+z, x and y are positive and y is negative. In all of the given options, the expression y - x + z is the only one which doesn't have the same signs. Hence it is not equivalent to x - y + z.