un - masculine singular
una -feminine singular
unos - masculine plural
unas - feminine plural
UN lápiz - a pencil
UNAS tareas - some homework
UNOS borradores - some erasers
UNAS mochilas - some backpacks
UNOS libros - some books
UNA calculadora - a calculator
UNOS papeles - some papers
UN examen - a test
Many times we can find the right article by paying attention to the noun ending:
unAS tareAS
unOS librOS
<span>Yo limpio mi carro.
</span>
Since <em>limpiar</em> is an -ar verb, when you conjugate it into the first person of the present tense, you simply replace the -ar ending with -o.
So, limpiar turns into limpio.