I'm so jealous of my brother's weeds right now. I saw this one in one of his previous pics and asked for better pixs. Don't recognize this one either so all help appreciated by both of us.

A potentilla perhaps
One that is common is mock strawberry, although there are many Cinquefoil (Potentilla) with yellow blooms. Whole plant image and leaves could help to confirm.

I'll tell him and have him check when he gets a chance. Thanks!!

It looks like a Buttercup (Ranunculus)

Yes Ranunculus (Buttercup) and Potentilla (Cinquefoil) can be very similar, especially in this case there is only bloom image, without clear details such as stamen, leaves or other parts.
in this case, I am inclined to potentilla based on sepals
Potentilla are member of Rosaceae and many of them have prominent sepals. sometime larger than the petals, green and often hairy
Ranunculus and many Ranunculaceae member usually not. Sepals mostly smaller than petals, often hidden behind petals, less hairy, and sometimes colored