N the United States, the average public school teacher currently earns an annual salary near $55,202. Reported national average salaries for the last six decades are listed below. Year National Average Teachers' Salary 1960 $4,995 1970 $8,626 1980 $15,970 1990 $31,367 2000 $41,807 2010 $55,202 Determine the average salary increase per year between the years 1980 and 1990. $1,539.70 $8,367.80 $2,566.20 $1,004.10

$1,539.70

Step-by-step explanation:

Given the data :

National average Teachers' salary (NATS)

YEAR:_1960 _ 1970 _ 1980 _ 1990 _ 2000 2010

NATS:4995_8626_15970_31367_41807_55202

AVEAGE SALARY INCREASE PER YEAR BETWEEN 1980 and 1990

Salary in 1980 = $15970

Salary in 1990 = $31367

Average salary increase per year:

Difference in salary / difference in years

$(31367 - 15970) / (1990 - 1980)

= $15397 / 10

= $1539.7

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".

56.6

step-by-step explanation:

the ratio of the perimeters is equal to the scale.

the ratio of the areas is equal to the square of the scale.

34 / 20 = k

a / 19.6 = k²

substituting:

a / 19.6 = (34 / 20)²

a = 19.6 (34 / 20)²

a ≈ 56.6