Three students were given the expression shown and were asked to take a common factor out of two of the terms.

Use the drop-down menus to complete the statements about whether each student's answer is an equivalent expression. Then choose an expression that is equivalent.

The expression is 4-9x+21.

The options for the drop downs are INCORRECT or CORRECT.
The other options for the drop down are HE FACTORED CORRECTLY, HE DID NOT DIVIDE 21 by -3 CORRECTLY, HE DID NOT DIVIDE -9x by 3 CORRECTLY, HE CANNOT SIMPLIFY 4-9x, HE CANNOT ADD -9x and 21, HE SHOULD HAVE FACTORED OUT 4 INSTEAD.

For the Equivalent expression the options are the numbers below.

PLZ HELP