I tried making lgx = y, but I can't get it to work.

Next problem is:

I managed to get it down to

but I don't know what next. The end result should be 16.

And what about these two:

and

What I did, was

Then, and that's where I'm stuck. What I get is: I can't get a squared y out of it. And I don't know how to deal with the fraction.

Please reply,

Thanks!