How to find log2 value, lo3, log5, log7 values I am asking proof of log2

If your pupose is for objective or multiple choice questions-

log 10=1; log 5+log 2=1; 0.5log 25+log 2=1; 0.5(log 2.5 + log 10)+ log 2=1;

Say log 2.5is nearly equal to log 2

Then, 1.5 log 2=0.5; *log 2=0.3