Use the echelon method to solve each system of two equations in two unknowns. Check your answers. 5. x + y = 5 2x - 2y = 2 7. 3x - 2y = -3 5x y = 2 9. 3x + 2y = −6 6. 4x + y = 9 3x - y = 5 8. 2x + 7y = -8 -2x + 3y = -12 10.-3x + y = 4 2x2y = -4 5x - 2y = -10 11. 6x - 2y = -4 3x + 4y = 8 12. 4m +3n = -1 2m + 5n = 3 14. 12s 5t= 9 81-18 13. 5p+11q = -7 3p8q = 25 3s 15. 6x + 7y=-2 16. 3a - 8b = 14 a - 2b = 2 18. 7x6y= 26 17. 3x + 2y = 5 6x + 4y = 8 19. 3x - 2y = -4 -6x + 4y = 8 9x - 5y = 1 -18x + 10y = 1 20. 3x + 5y + 2 = 0 9x + 15y + 6 = 0