b)[(6x-72):2-84]-28=5628
[(6x-72):2-84] = 5628+28
[(6x-72):2-84] = 596
(6x-72) = 596+84
(6x-72) = 680
6x = 680 +72
6x = 752
x =125,333....
b) là
[(6x-72):2-84]-28=5628
[(6x-72):2-84] =5628+28=5656
[(6x-72):2 =5656+84=5740
6x-72 =5740.2
6x-72 =11480
6x =11480+72
6x =11552
x =11552:6=1925,333....