Doesn't matter how you write it, there is no ambiguity. You read and solve from left to right prioritizing according to operation rank. If you write 6/2(2+1)=6÷2×(2+1)=6÷2⋅(2+1)=
This article shows that without additional brackets, some people may chose to change the order of the operations. But choosing that approach doesn't make it true though...