First, we use the logarithm property loga−logb=logba. Therefore,
log9−log8=log89 log81−log64=log6481 Then, the expression becomes
log6481log89 Now, we can rewrite the fraction 6481 as 8292=(89)2. So, the expression becomes
log(89)2log89 Using the logarithm property logab=bloga, we have log(89)2=2log89. Therefore,
log(89)2log89=2log89log89=21.