Firstly, you want to multiply (f^4)^2. 
Next, multiply everything on the numerator. 
Next, divide. 
Now remember that f^-2 = (1/f^2), so just convert the negative powered exponent to that, and your answer will be 
A squared + b squared = c squared
8.6^2+14.7^2=c^2
73.96+216.09=c^2
square root both sides and...
c=17.03085
Your answer is A
Hope this helps
Alright. For the first one, we must think, thirty percent of what number is equal to twelve? We can right that in equation form as