The first row of a section in a concert hall has 20 seats. the second row has 21 seats. the third row has 22 seats. this pattern continues and this section has 12 rows. how many seats are in this section?

To solve this problem you must apply the proccedure shown below:

1. The arithmetic sequence is:

Where is the nth termn, is the first term, is the common difference between the terms and is the number of the term.

2. Based on the information given in the problem, you have:

3. When you substitute these values into the formula, you obtain:

The answer is: seats

y = 0.77(x)

step-by-step explanation:

the jacket retains this value after 23% cut or retains 77% of original value. plug original 87 jacket price for x and the remaining value should be y.

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".