\(\dfrac{13}{6}+\dfrac{7}{4}=\dfrac{26}{12}+\dfrac{21}{12}=\dfrac{26+21}{12}=\dfrac{47}{12}\)

đoạn cuối sai sai...

\(7-x=7-\left(x-4\right)-4=3-\left(x-4\right)\)

để M ∈ Z \(\Rightarrow\) 7 - x ⋮ x - 4 \(\Leftrightarrow\) 3 - (x - 4) ⋮ x - 4

mà x - 4 ⋮ x - 4

\(\Rightarrow\) x - 4 ∈ Ư{3} = {-3; -1; 1; 3}

ta có bảng:

vậy x ∈ {1; 3; 5; 7}