Math
posted by Rayna .
1. the mystery shape has fawer than 3 lines of symmetry. 2. it has at least 1 pair of perpendicular sides. 3. it has at least 1 pair of parallel sides. 4. it has less than 1 obtuse angle.

Try a rectangle with adjacent sides of different length.
1. the mystery shape has 2 (fewer than 3) lines of symmetry.
2. it has 4 (at least 1) pairs of perpendicular sides.
3. it has 2 (at least 1) pair2 of parallel sides.
4. it has zero (less than 1) obtuse angle. 
I don't understand what you mean by try a rectangle with adjacent sides of different length.

"Try" because there may be more than one answer to this question. You have to be convinced that this is the right answer.
It may sound confusing, but the definition of a square is a rectangle with adjacent sides equal, therefore a square is a rectangle, which means that a rectangle can have adjacent sides equal (and becomes a square).
Think of the number of lines of symmetries of a square, and that of a rectangle (with adjacent sides of different lengths). See which one fits the first requirement.