Tìm x biết: x - 1/7 = 1/9

Bt1:
a; x-1/7=1/9
b;8/23×46/24-x=1/3
c;62/7× x=29/9÷3/26
d;1/5÷ x=1/5-1/7
Bt:2
a;A=n+3/n+1 la sô nguyên
b;B=n-5/n+2 la sô nguyên
c;C=2n+3/n+1 la sô nguyên