Data Sufficiency (DS) | Re: Is the area of the triangular region above less than 20?

when x and y are two sides of a square angle, the are is biggest.

if x side turn to right or to left, the area is smaller because the side y is the same and h of the triangle is smaller.

if x+y<13 this mean x, y < 6 and 7
6x7=42= tw time the area
so, combine two statement, xy<21
we
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