Hello. You correctly wrote the following property, but you made a mistake when you applied it.
log(an) = n∙log(a)
We see on the left-hand side (above) that n is the exponent.
log(5t/2)
That is, the base is 5 and the exponent is t/2.
In the symbolic expression log(an), we have a=5 and n=t/2.
Therefore, what is n∙log(a) ?
?