Ms. johnson asked her class to write an equivalent expression to 14d - 9 + 21k - 7dk + 2. riley wrote the expression 7dk(2 - 3 - 1) _ 7 ahmad write the expression 7(2d + 3k - dk) - 7 ariana wrote the expression 7k(2d - 3 - d) - 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 + 2
Please check this solution:
7(2d + 3k - dk) - 7 = 14d - 9 + 21k - 7dk + 2
7(2d + 3k - dk) - 7 = 14d + 21k - 7dk -9 + 2
7(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 + 2
We simplify it to:
7(2d + 3k - dk) - 7 = 14d + 21k - 7dk -7
7 * 2d = 14d
7 * 3k = 21k
7 * - dk = -dk

Therefore, 
7(2d + 3k - dk) - 7 is equal to 14d + 21k - 7dk -7

In all honesty, there really is no “work” per say to show. mainly it’s just using the process of elimination. the question is asking which domain(s) would be the most appropriate for the function c(n). n is the number of observed vehicles so right away, 1, 2, and 3 can be eliminated.why? 1, 2 start in the negatives and therefore it is impossible to observe negative cars. so, #4 would be the best answer to the given problem.