19. 21x + 6 = 90
x = 4
20. 11x - 2 + 75 = 180
x = 9.727272727
21. 8x - 4 = 60
x = 8
22. x + 139 = 132
x = -7
23. -1 + 14x = 12x + 17
x = 9
24. 21x + 5 = 23x - 5
x = 5
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