m<3 =72°
This is because m<1 and m<3 are vertically opposite.
Symmetric property of an Equality
The practical rule would be, times that number, by the result of the first time you multiplied the first number. But, it would all depend by how much your're raising the number by.
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For example:</u>

We do,

But, once again, this was an example. This would show and illustrate the rule of "raising a power".<span />
If the perimeter is 182, double the length which is 52 to get 104. Subtract that from 182 to get 78. Divide that by 2 to get the width which is 39.