36.
If $${\log _{10}}7 = a,$$   then $${\log _{10}}\left( {\frac{1}{{70}}} \right)$$   is equal to -

37.
If $$\log x - 5\log 3 = - 2,$$     then x equals -

38.
If $$a = {b^2} = {c^3} = {d^4},$$    then the value of $${\log _a}\left( {abcd} \right)$$   would be -

39.
If $${\log _3}x + {\log _{\underline 9 }}{x^2} + {\log _{27}}{x^3}$$     $$ = 9,$$  then x equals to -

40.
If $${\log _7}{\log _5}\left( {\sqrt {x + 5} + \sqrt x } \right)$$     $$ = 0,$$  what is the value of x ?