State the reason why k = m given: klmn is a parallelogram.

If KLMN is a parallelogram, then that means it must have only 4 sides and the opposite sides must be parallel.
For example;
A square, rectangle or rhombus.
A square has 4 equal sides, having the length's and width's opposite sides being parallel.
A rectangle has 2 pairs of equal sides; lengths and widths. The lengths or widths will be double the adjacent side.
A rhombus, similar to a rectangle, has 2 equal pairs of sides.

If K = M in Parallaleogram KLMN, then it must apply to one of the examples above.

I hope this helps!

3x+9+4x+x=8x+9that's the answer for your question.