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