Three students were given the expression shown and were asked to take a common factor out of two of the terms.
 4-9x+21
 Chang: 4-3(3x+7)
 Chang’s expression is ___ because _______.
 Benjamin: 4+3(3x+7)
 Benjamin’s expression is ___ because ________.
 Habib: 4+12x
 Habib’s expression is ___ because ________.
 Equivalent Expression
 The correct simplification of this expression _____.
 please help me omg