Answer:
18. m<EBC = 43°, m<CBD = 47°
19. m<EBC = 50°, m<ABC = 130°
Explanation:
18. Find m<EBC and m<CBD
m<EBC = (5x + 8) and m<CBD = (6x + 5)
these two angles add up to a right angle, therefore their sum is 90°
5x + 8 + 6x + 5 = 90
11x + 13 = 90 , 11x = 77 , x = 7
m<EBC: 5(7) + 8 = 43
m<CBD: 6(7) + 5 = 47
19. Find m<EBC and m<ABC
m<EBC = (3x + 20) and m<ABC = (17x - 40)
these two angles are supplementary, meaning that they add up to 180°
3x + 20 + 17x - 40 = 180
20x - 20 = 180, 20x = 200, x = 10
m<EBC: 3(10) + 20 = 50
m<ABC: 17(10) - 40 = 130