1) answer is x = 4. (simply divide both sides by 4 and simplify)
(2) answer is t = 16 (just simplify, multiply both sides by 4, multiply 12 x 4, divide both sides by 3, and simplify again.)
(3) answer is r = 13 (subtract 5 from both sides, subtract 31 - 5, divide both sides by 2, and simplify fraction)
(4) answer is n = 7 (add 7 to both sides, add 21 + 7, divide both sides by 4, and simplify fraction again)
(5) answer is a = 12 (subtract 2 from both sides, subtract 6 - 2, multiply both sides by 3, and multiply 4 x 3 and u get 12)
(6) answer is y = 40 (add 8 to both sides, add 2 + 8, multiply both sides by 4, multiply 10 x 4 and u get 40)
