Failing

I watch my brothers kids whenever him and his wife are at work. I keep them from like 3 when he gets out of school until 11 pm. One of the boys is not doing so good in math and I wanna help find a way to make studying easier while I’m watching him besides flash cards. He loves video games I thought maybe theres a website you parents know or a trick to help him learn his multiplication better? Any advice is greatly appreciated! He’s in 3rd grade btw