If $$ {0.7\over 1-6c}=-0.2$$ then what is the value of c.

The value of   $${(75.8)^2-(55.8)^2\over20}$$

$$ \sqrt{0.00004761} $$   equal to

If $${a+b=10}$$ and $$ \sqrt{a\over b}-13=-\sqrt{b\over a}-11$$, then what is the value of $${3ab+4a^2+5b^2}$$?

Simplify  $$ ^{3}\sqrt{-2197} × ^{3}\sqrt{{-125}} \ ÷ ^{3}\sqrt{27\over512}$$.

Direction: what should come in place at question mark(?).

$$ {\sqrt{4489}+(71)^{2}-(?)^{2}=2707}$$

Evaluate: $${-(4-6)^2-3(-2)+।-6।\over 18-9÷3×5}$$

If $$ {y={2x-1\over x+3}}$$ find x when y=1