Is this fair pricing?

I mow my Grandmothers lawn once a week, it is a 1/2 acre, and i use an old push mower (self propelled) it has a sorta slant up, and i do bag it. I am experienced in mowing lawns (since i was 11) so i do a decent job. I am a 14 year old girl, and i also weedwack it for her, she pays me $25. Is that good, or should i ask for more?