Hint: We can find all 3 angles in the triangle.
Once we know the angle that's next to x, we can use the rule that says "angles on a line add to 180 degrees"

Cheers,
Brent

Hi didieravoaka,

Any time a Quant question includes a triangle, that triangle is almost always a part of how you have to answer the given question.

When dealing with criss-crossing lines, it's important to remember that opposite angles are EQUAL and the angles on one side of a line always add up to 180 degrees. Knowing those two rules...

1) In the upper 'right corner', we have 40/140/40/140
2) At the bottom, we have 130/50/130/50

3) We now know two angles in the triangle: 40 and 50, so the third angle in that triangle is 90. Since angles on one side of a line always add up to 180, we now know that X=90.

Final Answer: A

GMAT assassins aren't born, they're made,
Rich

didieravoaka wrote:Thanks guys your posts are really helpful. But why we don't use the rule that says, " Angles that are on the alternate interior sides of the transversal are equal" ?

Yes, but that applies only to parallel lines.

Cheers,
Brent