"A gusto" rather than "agusto"?

Question

Following your hint, I tried to use "agusto" as an adjective. On being marked wrong, I looked to see what options my dictionary allowed, but I could not find any noun or adjective spelled that way. A gusto o Agusto - Diccionario de Dudas > https://www.diccionariodedudas.com/a-gusto-o-agusto throws some light on the puzzle. But if we use "a gusto", should we rather write: "Cómo a gusto nos hemos sentido" - would that also be OK?

Accepted Answer

Hola David
There is a typo in that exercise, "a gusto" is written separately, not together. We will be correcting that shortly. 
So, we use it to express that you are "enjoying and relaxed" in a specific situation, or it could also mean "happily, willing", for example:

Los niños están muy a gusto ahí en el jardín. 
The kids are happy and relaxed there in the garden.

A veces tengo que hacer algunas horas extra, pero, la verdad es que lo hago a gusto, porque me encanta mi trabajo.
I sometimes have to do some extra hours, but, to be honest, I do it happily, because I love my job.

Colloquially, we also use it to say that someone is a bit tipsy when drinking:

Mira qué a gusto está Miguel, después de un par de copas. 
Look how chilled (~tipsy) Miguel is, after a couple of drinks.

Your suggestion using "cómo" would only work if you say:
"Cómo nos hemos sentido de a gusto"
Saludos
Inma