Question

the Function h(m)=-3/20m+12 Describes the height of a 12-inch candle after it has been burning m Minutes. How many minutes has a 12-inch candle been burning, if it is now 7.5 inches high.

Answer 1

h(m) should be read as "height, as a function of minutes"
or
h(m) means "the height of the candle after m minutes have passed"

In this case you're looking for the height (which is in inches) so that means

h(m) = 7.5

Your goal is to find the number of minutes so...

7.5 = -3/20m+12

Answer 2

how do you solve that?

Answer 3

It is a linear equation. Sometimes called a "two step" equation.

7.5 = -3/20m+12
7.5 -12 = -3/20m+12 -12 subtract 12 from both sides
-4.5 = -3/20m + 0
-4.5 = -3/20m
(-4.5)*20 = (-3/20)*20m multiply both sides by 20
-90 = -3m
-90/-3 = -3m/3 divide both sides by 3
30 = m


You may say "um, you did THREE steps..." but multiplying by 20 and dividing by 3 can be done in a single step... just multiply by -20/3 and that's it.

Answer 4

thank you.

Answer 5

You're welcome. :)