Hi there!
6/7 itself is already simplified in it's smallest form.
6/7 = 6/7.
In a decimal form this is 0.857143.
Hope this helps!
The following information will help us with this problem:
![\sqrt[m]{x^n} = x^{\frac{n}{m}](https://tex.z-dn.net/?f=%5Csqrt%5Bm%5D%7Bx%5En%7D%20%3D%20x%5E%7B%5Cfrac%7Bn%7D%7Bm%7D)
When we use that information in the context of this problem, we can find:
![\sqrt[4]{15^7} = 15^{\frac{7}{4}}](https://tex.z-dn.net/?f=%5Csqrt%5B4%5D%7B15%5E7%7D%20%3D%2015%5E%7B%5Cfrac%7B7%7D%7B4%7D%7D)
Thus, a = 15, b = 7, and c = 4.
Anyway
2pi radians=360
so
-4pi/9radians=xdegrees
2pi/360=-4pi/9r/x
times both sides by 360x
2xpi=-1440pi/9
2xpi=-160pi
divide both sides by 2pi
x=-80
80 degres
-2 is the correct answer.