Question 544579
{{{(3a/(a-4))-(4/(3(a-4)))}}}

{{{(3/3)(3a/(a-4))-(4/(3(a-4)))}}} multiplied by a 1/1, 3/3=1
{{{(9a/(3(a-4)))-(4/(3(a-4)))}}}both have common denoms so subtract numerators
{{{(9a-4)/(3(a-4))}}}