log3(1000)-log5(500)-log7(100)?
log10(1000)=3; log10(500)=2.6990 (approx); log10(100)=2.
log10(3)=0.4771 (approx); log10(5)=0.6990 (approx); log10(7)=0.8451 (approx).
logb(a)=log10(a)/log10(b).
So the original expression becomes:
3/0.4771-2.6990/0.6990-2/0.8451=0.05977 approx.