Answer:
24 ft
Explanation:
Let the height of the lantern = x.
Set the ratios:
Ratio of the lantern & shadow: (x/72)
Ratio of the man & shadow: (6/18)
*Note: Remember to consistently set the ratio. For me, I set it as the thing/man over the shadow. You can do the opposite, but both must be the same either (thing/person)/shadow, or shadow/(thing/person).
Set the ratios equal to each other, and cross multiply
(x/72) = (6/18)
(18x) = (6 * 72)
18x = 432
Isolate the variable, x. Note the equal sign, what you do to one side, you do to the other. Divide 18 from both sides:
(18x)/18 = (432)/18
x = 432/18
x = 24
24 ft is the height of the lightpost.