<span>No.
From the data provided you can not determine what the standard deviation is. In order to determine the standard deviation you need the actual grades not just a mean.</span>
<span> zeros of the quadratic function when f(x) = 0
so
</span><span>8x^2 – 16x – 15 = 0
(8x + 5)(x - 3) = 0
8x + 5 = 0; x = -5/8
x - 3 = 0; x = 3
Answer
x = -5/8 and x = 3</span>
Those two angles total equal 180 degrees.
Since we know the first angle equals 155 degrees.
180-155+25.
ABC is 25 degrees.
