Which expression is equivalent to (3a)-^2?

It’s the first one... it literally says that.
but here’s why!
okay so when a exponent is negative
(like as we have here... -2)
it means you gotta put it as a fraction
so like 6 would be 1/6
and 3 would be 1/3
then you square it!
so 6 would become 1/36
and 3 would become 1/9
also the a would be a^-2
but to make it positive you put it on the other side of the fraction if that makes sense :)