How to apply more than one value to 1 variable?

example:
basebet = balance/10000
nextbet = basebet
x= 5,10,11,18,25
chance = 90

function dobet()
x= 5,10,11,18,25,63,99,548
counter+=1
if counter == x then
chance = 49.5
else
chance = 90
end

I was wondering if there is only how to bet when the counter is equal to x, being some value that I put inside x