1) log2(x - 2) , when x = 10
log2 (10 - 2)
= log2 (8)
now we know that,
loga (b) = log b/ log a
so, = log 8/ log 2
= log (2)³/ log 2
we also know, log (a)^b = b log (a)
so,
= 3 log 2/ log 2 = 3
2) 6 r^t + 63 , when r = 4 and t = 2
so putting values,
6(4)² + 63
= 6(16) + 63
= 96 + 63 = 159
3) log25 (x) , when x = 5
log25 (5)
= log 5/ log 25
= log 5 / log (5)²
= log 5/ 2 log 5
= 1/5
Hope it helps...