Problem Solving

X-Y > 10, is x-y > x+y?

1. x = 8
2. y= -20

The answer is D.

Anyone care to explain?

If X-Y > 10, is x-y > x+y?


Statement 1: x=8

Plug 8 into the first equation:
8-Y > 10

In order for 8-Y to be greater then 10, Y must be a negative number.

Plug 8 and (-Y) into the second equation:
8 - (-Y) > 8 + (-Y), this becomes:

8+Y > 8-Y

[spoiler]From this we can see that 8+Y is greater the 8-Y
Sufficient[/spoiler]

Statement 2: y= -20

Plug -20 into first equation:
x-(-20)>10
X+20>10

X-(-20) > X+(-20), which becomes:

X+20 > X-20

[spoiler]From this we can see that for any value of X, X+20 will be greater then X-20
Sufficient.
Both Sufficient, Choose D[/spoiler]

This question is much easier if you simplify the question before you attack the statements.

x-y>x+y --> -y>y
The question becomes is -y>y, which is only possible if y is negative. So the real question becomes "Is y<0?"

Makes it easier to assess the statements.