Khan academy has a lot on this sorry I couldn't answer bro
Divide the figure into known figures like rectangle and semi-circle
Calculate the area of the whole figure by adding the area of the separate figures
So final step to do is you square root the x^2 and square root the 4000 which will get you answer of x = 63.2455532034 which can be 63.2. Hope this help!!
The missing justification is for the statement that three angles add to a particular angle. The appropriate choice is ...
... c. Angle Addition Postulate
