$12 \frac{5}{7} + 23 \frac{3}{5} - 14 \frac{1}{3} = 28 \frac{4}{7} - ?$

If $x + \frac{1}{x} = \sqrt{13}$,then $\frac{3x}{x^2 - 1}$ is equal to:

The value of $\frac{2 \frac{1}{3}-1 \frac{2}{11}}{3+\frac{1}{3+\frac{1}{3+\frac{1}{3}}}}$ is

If $x^{2} + \frac{1}{x^{2}} = 1$,then what is the value of $x^{48} + x^{42} + x^{38} + x^{30} + x^{24} + x^{18} + x^{12} + x^{6} + 1$?

If $a, b, c$ are three non-zero real numbers such that $a+b+c=0$ and $b^{2} \neq ca,$ then the value of $\frac{a^{2}+b^{2}+c^{2}}{b^{2}-ca}$ is

While selling,a businessman allows $40 \%$ discount on the marked price and there is a loss of $30 \%$. If it is sold at the marked price,the profit percent will be: