678 x 91 - 678 xa = 678
678 x ( 91-a ) =678
91 -a = 6780:678
91-a = 10
a = 91-10
a = 81
vậy a=81
678*91 -678*a = 6780 thi a = 81 vi 91-81= 10 ma 10*678 =6780 vay thoai man dau bai
=678.[91-a]=6780
91-a=6780:678
91-a=10
a=91-10
a=81
678 x 91 - 678 x a = 6780
=> 678 x (91-a) =6780
=> 91-a = 6780:678
=> 91-a = 10
a= 91-10
=> a=81
Ủng hộ nhé
