The unknown digit is 7 because 6.471 is greater than 6.470 and less than 6.48.
Basically this app helps you with any question you need you got to ask a question and people will answer it for you just like i am doing now also you can answer other peoples questions to get points.
Is this 9x+4=5+5x or is it 9x•4=5•5x?
both the surface areas of the green and blue figures?
