18,19,20,21,23 please help me. I really need this answer.please help me.

Answer:18. Supplementary19. Vertical20. x = 723. x = 25Step-by-step explanation:Use angle relationships to make equations which you can solve for x.Example:18. These two angles form a line. These are called supplementary.19. These angles are across a vertex from each other and are equal or the same.20. 9x + 1 = 7x - 9 + 5x - 11 9x + 1 = 12x - 209x - 9x + 1 = 12x - 9x - 20               1 = 3x - 20       1 + 20 = 3x - 20 + 20             21 = 3x               7 = x23. These two angles are across a vertex from each other. This means the angles are equal. Think of it as a reflection. If you folded the paper on that vertex, the lines would be in the exact same place.So set the two expressions equal to each other. Then use inverse operations to isolate x and solve.5x + 4 = 8x - 715x - 5x + 4 = 8x - 5x - 714 = 3x - 714 + 71 = 3x - 71 + 7175 = 3x25 = x