(i) formula --- log a + log b (with common base) = log(ab)

log2+ log5 = log 2*5=log 10 = 1

(ii) formula --- log a + log b - log c = log (ab)/c (with common base)

log4+ log5 - log2 = log (4*5)/2= log 20/2 = log 10 = 1

(iii) formula --- b log a = log a tothe power b (with a common base)

= log (5 square * 8 )/4 raised to half

a raised to half =root of a

=log (25*8)/2

= log 200/2=x

10 raised to x = 100

x=2

(NOTE :- ALL BASES HAVE NOT BEEN MENTIONED HERE. THE BASES OF THESE COMMON LOGARITHMS ARE ASSUMED TO BE 10)