A^2-9b^2/3ab :(1/3b -1/a) A=8 4/7 B= 4 1/7

[latex]\frac{a^2-9b^2}{3ab} :(\frac{1}{3b} -\frac{1}{a})=\frac{(a-3b)(a+3b)}{3ab}:\frac{a-3b}{3ab}=\frac{(a-3b)(a+3b)}{3ab}*\frac{3ab}{a-3b}=\\=a+3b[/latex] [latex]a=8\frac{4}{7}=\frac{60}{7}\\b=4\frac{1}{7}=\frac{29}{7}\\a+3b=\frac{60}{7}+3*\frac{29}{7}=\frac{147}{7}=21[/latex]