Answer:
20. x = 5, y = -2
21. x = 11, y = 12
22. x = 22, y = 11
23. x = 11, y = 10
Step-by-step explanation:
20. Opposite sides in the parallelogram are congruent, so

Solve this system of two equations:

Multiply the first equation by 2 and add two equations:

Substitute it into the first equation:

21. Opposite angles in the parallelogram are congruent, so

Consecutive angles are supplementary, so

Solve this system of two equations:

From the second equation

Substitute it into the first equation:

22. Opposite angles in the parallelogram are congruent, so

Consecutive angles are supplementary, so

Solve this system of two equations:

From the first equation

Substitute it into the second equation:

23. Opposite sides in the parallelogram are congruent, so

Solve this system of two equations:

Multiply the second equation by 2 and subtract it from the first equation:

Substitute it into the first equation:
