Ms. johnson asked her class to write an equivalent expression to 14 − 9 + 21 − 7 + 2.  riley wrote the expression 7(2 − 3 − 1) − 7  ahmad wrote the expression 7(2 − 3 − ) − 7  ariana wrote the expression 7(2 − 3 − ) − 7 who is correct? explain how you know.

Ahmad wrote the correct expression.To prove that 7(2d + 3k - dk) - 7 is equal to 14d - 9 + 21k - 7dk + 2Please check this solution:7(2d + 3k - dk) - 7 = 14d - 9 + 21k - 7dk + 27(2d + 3k - dk) - 7 = 14d + 21k - 7dk -9 + 27(2d + 3k - dk) - 7 = 14d + 21k - 7dk -7
Get the common variable which is 7.7(2d + 3k - dk) - 7 = 7(2d + 3k - dk) - 7
For checking, we can simplify the equation...from 7(2d + 3k - dk) - 7 = 14d - 9 + 21k - 7dk + 2We simplify it to:7(2d + 3k - dk) - 7 = 14d + 21k - 7dk -77 * 2d = 14d7 * 3k = 21k7 * - dk = -dk
Therefore, 7(2d + 3k - dk) - 7 is equal to 14d + 21k - 7dk -7
                                hope it helps