If a square mirror has a 30-inch diagonal, what is the area of the mirror, in inches

You can find the length of a side by using the Pythagoras theorem
Let x be length of each side then:-
2x^2 = 30^2
x^2 = 900/2 = 450
area  = length of one side squared:-
area = x^2 = 450 ins^2  < Answer

Byou start by adding them all and setting them equal to 180 since that is half of the total degrees in a circle.(2x+8) + (3x-14) + (3x-14) = 1808x-20 = 1808x = 200x = 25