A stack of boards is 21 inches high. The boards are 1 3/4 inches thick. How many board are there?

How do i make someone brainliest? (if you answer me, i might be able to make you brainliest! )

Identify the number as a rational or irrational.explain. 127

Which expression demonstrates the use of the commutative property of addition in the first step of simplifying the expression (-1+i)+(21+5i)+0