A. us phone numbers traditionally do not start with a zero or a one, otherwise there are no other restrictions, so how many 7 digit phone numbers are possible?

b. some cities have now required you to dial area codes first. for example in chicago we either dial 773 or 312, so now how many possible chicago phone numbers are there?

c. why have cities and suburbs have added on these area codes in recent years?

he used the algebra tiles correctly.

step-by-step explanation:

given : 3x(2x-1)

solution :

since he used algebra tiles .

armando's solution is the same in the solution shown in figure

as he distributed 2x into x and x and wrote them vertically

and also write   -1 vertically

and 3x into x and x and x and wrote it horizontally

performing the multiplication in the algebra tiles we get

and solving the given expression :

3x(2x-1)

since solving the expression using tiles   and solving the expression algebraically we get the same answer

thus   we can choose the first statement as the answer to this problem which is "he used the algebra tiles correctly".