Using multiple conditions with findfirst() in Julia

Say I have two arrays like so:

• x = [10, 30, 50, 99, 299]
• y = [3, 29, 30, 23, 55]

How can I find the index where both following conditions are satisfied?

• x > 80 & y > 30

So for my example, I expect the return would be index 5. I imagine the format would look something like this:

findfirst(x -> x > 80 \union y -> y> 30, x,y)

but this doesnt work..

Also in my case x and y are columns in a dataframe, but doing an index search also doesnt work..

Broadcasting seems to work: findfirst((x .> 80) .& (y .> 30))