For addition of two unlike fractions,first change them to the like fractions. LCM of 9,12=36 Now,let us change each of the given fraction into an equivalent fraction having 36 as the denominator. $$\dfrac{8}{9}\times \dfrac{4}{4}=\dfrac{32}{36}$$
$$\dfrac{7}{12}\times \dfrac{3}{3}=\dfrac{21}{36}$$ Now.add the like fractions, $$=\dfrac{32}{36}$$$$+\dfrac{21}{36}$$