6.
If $${\log _{10}}7 = a,$$   then $${\log _{10}}\left( {\frac{1}{{70}}} \right)$$   is equal to

7.
If log10 2 = 0.3010, then log2 10 is equal to:

8.
If log10 2 = 0.3010, the value of log10 80 is:

9.
If $${\log _{10}}5 + {\log _{10}}\left( {5x + 1} \right)$$     = $${\log _{10}}$$ $$\left( {x + 5} \right)$$ $$\, + $$ $$1,$$ then x is equal to :

10.
The value of $${\frac{1}{{{{\log }_3}60}} + }$$  $${\frac{1}{{{{\log }_4}60}} + }$$  $${\frac{1}{{{{\log }_5}60}}}$$   is :