Solve each equation. if an equation has no solutions or if an equation has infinitely many solutions, explain how you know. 15. 3x − x − 5 = 2(x + 2) − 9 16. 7x − 3x + 7 = 3(x − 4) + 20 17. −2(x − 2) − 4x = 3(x + 1) − 9x 18. 5(x + 2) − 3 = 3x − 8x + 7 19. 4(x + 3) − 4 = 8x + 10 − 4x 20. 3(x + 2) + 4x − 5 = 7(x + 1) − 6