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.

I don't understand what you mean by try a rectangle with adjacent sides of different length.

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.

"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.

I still don't understand

Based on the given conditions, we can analyze each statement and eliminate shapes that do not satisfy all the requirements to find the mystery shape.

1. "The mystery shape has fewer than 3 lines of symmetry": A line of symmetry divides a shape into two equal halves, such that if the shape is folded along the line, both halves will perfectly match. Since the mystery shape has fewer than 3 lines of symmetry, we can eliminate regular polygons, such as triangles, squares, and hexagons, as they have more than three lines of symmetry.

2. "It has at least 1 pair of perpendicular sides": This narrows down our options to polygons with at least one right angle. Shapes like rectangles and squares meet this requirement.

3. "It has at least 1 pair of parallel sides": From the previous statement, we already have rectangles and squares in consideration, which have two sets of parallel sides.

4. "It has less than 1 obtuse angle": An obtuse angle measures more than 90 degrees. Since the mystery shape should have less than 1 obtuse angle, we can rule out rhombuses or non-right triangles.

Putting all the conditions together, the mystery shape can be determined as a rectangle or a square, as they both meet all the given criteria.