[tex] 1)\frac{3}{m} +\frac{5}{n} 2)\frac{4}{x} -\frac{3}{xy} 3)\frac{7}{9ab} -\frac{13}{12ab} [/tex]помогите пж

3/m + 5/n = (3n + 5m)/(mn)

4/x - 3/(xy) = (4y - 3)/(xy)

7/(9ab) - 13/(12ab) = (28 - 39)/(36ab) = -11/(36ab)

1) 2) 3)