$1.2 \times 1.02 \times 1.002 = ?$

If the numerator of a fraction is increased by $2$ and the denominator is increased by $3,$ the fraction becomes $\frac{7}{9},$ and if both the numerator and the denominator are decreased by $1,$ the fraction becomes $\frac{4}{5}.$ What is the original fraction?

What should come in place of the question mark $(?)$ in the following equation?
$30.01^{2} - 19.98^{2} - ? = 21.81^{2}$

If $(x+\frac{1}{x})^{2}=3$,then the value of $(x^{72}+x^{66}+x^{54}+x^{36}+x^{24}+x^{6}+1)$ is

$3 \frac{1}{4} + 2 \frac{1}{2} - 1 \frac{5}{6} = \frac{(?)^{2}}{10} + 1 \frac{5}{12}$

If $a^{2}+b^{2}-c^{2}=2(a-b-c)-3,$ then the value of $4a-3b+5c$ is