I'm having a hard time on this problem. plz . will mark brainliest.
find the value of y.
-20
-87
-31
-42

Step-by-step explanation:

We know: opposite angles in a parallelogram have the same measure.

Therefore we have the equation:

           subtract y from both sides

We know: the sum of the angle measures in the triangle is 180°.

Therefore we have the equation:

         subtitute x = 87

             subtract 149 from both sides

since your problem is x^4 = 81, what you have to undeo is the "to the fourth power" part.

the inverse (opposite operation) of "to the fourth power" is "to the fourth root".

  (x^4) ^ ¼   = 81 ^ ¼  

  81 = 3^4     so (3 ^ 4) ^ ¼   =   3 ^ 1   = 3

by hand: (3 ^ 4) ^ ¼   =   3 ^ (4 x ¼) = 3 ^ 1   = 3   (when you take a power to a power, multiply the exponents.)

or, do it by calculator. one way of finding the fourth root is to use ^ (1/4)

step-by-step explanation:

the answer is b.

64

step-by-step explanation:

c=2πr=2·π·8≈64