7) Use cummutative law to find an equivalent expression.

73+yz
Answer: 73(y+z) I know this one is wrong but I cannot figure out how to do the problem.

8) Simplify
6[5-9(3-1]
Answer: -70

10)The formula b=30a is used in New England to estimate the minimum furnace output, b, in BTU's for a modern house with a square feet of flooring.
A) determine the minimum furnace output for a 2100 ft squared modern house.
B) solve formula for a
Answer:a) 630,000
b) unsure how to calculate

7) To use the commutative law to find an equivalent expression for 73 + yz, we need to switch the positions of the terms to show the commutative property.

The commutative property states that for any real numbers a and b, a + b = b + a.

Therefore, 73 + yz can be rewritten as yz + 73.

8) To simplify 6[5 - 9(3-1)], you need to follow the order of operations, which is parentheses, exponents, multiplication and division (from left to right), and addition and subtraction (from left to right).

First, simplify the expression inside the parentheses: 3 - 1 = 2.

Next, multiply 9 by 2: 9(2) = 18.

Now, substitute the simplified expression into the original expression: 6[5 - 18].

Continue simplifying within the square brackets: 5 - 18 = -13.

Finally, multiply 6 by -13: 6(-13) = -78.

Therefore, the simplified expression is -78.

10)

a) To determine the minimum furnace output for a 2100 ft squared modern house, we can substitute the value of a (2100) into the formula b = 30a.

b = 30 * 2100 = 63000 BTU's

Therefore, the minimum furnace output for a 2100 ft squared modern house is 63000 BTU's.

b) To solve the formula b = 30a for a, we need to isolate the variable a.

Divide both sides of the equation by 30:

b/30 = a

Therefore, the formula for a is a = b/30.

7) To use the commutative law to find an equivalent expression for 73 + yz, you need to rearrange the terms in a different order. The commutative law states that you can change the order of addition or multiplication without changing the result.

In this case, 73 + yz can be rearranged as yz + 73. So the equivalent expression would be yz + 73.

8) To simplify 6[5 - 9(3 - 1)], you need to follow the order of operations, which is parentheses, exponents, multiplication/division (from left to right), and addition/subtraction (from left to right).

First, simplify the expression inside the parentheses: 3 - 1 = 2.

Next, simplify the expression inside the square brackets: 5 - 9(2). Since multiplication comes before subtraction, we need to evaluate 9(2) first: 9 * 2 = 18. So we have 5 - 18.

Finally, complete the subtraction: 5 - 18 = -13.

Now, multiply the result with 6: 6 * (-13) = -78.

So the simplified expression is -78.

10)
a) To determine the minimum furnace output for a 2100 ft^2 modern house using the formula b = 30a, you substitute the value of a into the formula.

b = 30 * 2100 = 63,000 BTU's

So the minimum furnace output for a 2100 ft^2 modern house is 63,000 BTU's.

b) To solve the formula b = 30a for a, you need to isolate the variable a.

Divide both sides of the equation by 30:

b/30 = a

So the formula to calculate a would be a = b/30.