B
is fine you just write d = r*t and then divide both sides by t to get d/t = r
C
is fine as well. You need only divide both sides by r to get
r*t = d
rt/r = d/r
t = d/r
D
D is fine. All you have done is interchanged r and t. That's called the associative property of multiplication.
A
is the one that is not correct.
A <<<< Answer
