Hey! Here are 6 easy ways to choose a maths tutor:

Formal maths qualifications. You’d think this would go without saying, but many parents rely on a relative to provide much-needed maths tuition informally.
Teacher training.
Location and availability.
Student-teacher ratio.
Exam preparation.
Choose a maths tutor offering the right pricing.

But to make your task as easy as possible, I recommend looking at these math websites 4th grade.
Here you can find one or more great math tutors who can explain any math topic to your brother.