I need the help for algebra II ....?

Question

my direction say

Use properties and definitions of operations to show that the statemen is true. Justify the step.

- 15 * (3 / b) = 45 / b

-(a + b) -c = a + (b - c)

-(12b + 15) -3b = 15 + 9b

& i also have a question that is confusing

- the elevator in the washington monument takes 60 seconds to rise 500 feet. What is the average speed in miles per hour?

Answer 1

whoa -- it took me awhile to figure out that " - " in front of your problems wasn't a minus sign!  be careful about things like that.

15 * (3/b) = 45/ b

associative property:

(15*3)/b = 45/b

multiplication:

45/b = 45/b

(a + b) - c = a + (b - c)

associative property -- changes the grouping around +

(12b + 15) - 3b = 15 + 9b

commutative property changes order around +:

(15 + 12b) - 3b = 15 + 9b

associative property changes grouping:

15 + (12b - 3b) = 15 + 9b

subtraction:

15 + 9b = 15 + 9b

last question:  500 ft per 60 seconds

= 500ft/60sec (1mi/5280ft)(60sec/1min)(60min/1hr)

= (500x1x60x60)(60x5280x1x1)miles/hour

= approximately 5.68 miles per hour

that's it! ;)