Câu 1 :
4/7 . x - 2/3 = 1/5
4/7 . x = 1/5 + 2/3
4/7 . x = 13/15
x = 13/15 : 4/7
x = 91/60
Câu 2 :
2/3 + 1/3 : x = 1
1/3 : x = 1 - 2/3
1/3 : x = 1/3
x = 1/3 : 1/3
x = 1
Câu 3 :
x/5 - 5/6 = 11/30
x/5 = 11/30 + 5/6
x/5 = 6/5
=> x = 6
Câu 4 :
6/7 + 1/7 x 2/7 + 1/7 x 5/7
= 6/7 + 2/49 + 5/49
= 6/7 + 7/49
= 6/7 + 1/7
= 1
Câu 5 :
6/7 + 5/7 : 5 - 8/9
= 6/7 + 1/7 - 8/9
= 1 - 8/9
= 1/9