5.2a Laws of Logarithms (Example 3)

Example 3

Given that ${\log }_{7}4=0.712$   and ${\log }_{7}5=0.827$  , evaluate the following.
(a) ${\log }_{7}20$
(b) ${\log }_{7}1\frac{1}{4}$
(c) ${\log }_{7}0.8$
(d) ${\log }_{7}28$
(e) ${\log }_{7}140$
(f) ${\log }_{7}100$
(g) ${\log }_{7}0.25$
(h) ${\log }_7\frac{35}{64}$