h = the number of hours
72 - 0.6h = 68.4
[The temperature was 72°F and it drops/decreases 0.6°F per hour(h), and the current temperature = 68.4°F]
To find h, isolate/get the variable "h" by itself in the equation:
72 - 0.6h = 68.4 Subtract 72 on both sides
72 - 72 - 0.6h = 68.4 - 72
-0.6h = -3.6 Divide -0.6 on both sides to get "h" by itself
[tex]\frac{-0.6h}{-0.6} =\frac{-3.6}{-0.6}[/tex] (two negative signs cancel each other out and become positive)
h = 6 6 hours have passed
