The two angles are supplementary angles, which when added together equal 180 degrees.
6x -10 + 6x +10 = 180
Combine like terms:
12x = 180
Divide both sides by 12:
x = 180/12
x = 15
The answer is C) 15
LCD is least common denominator. So looking at the denominators, their factors are...
First term x^2 - 5x + 4 = (x - )( x - ). We know this because the 4 (c term)is + so both signs are the same, and both are NEGATIVE because 5 (b term) is -
= (x - 4)(x - 1) because(-1)(-4) = 4 (c term) and -1 + -4 = -5 (b term)
We cannot calculate the confidence interval without the sample size. However, for the second question, the sample size needed would be 49.
The formula we use is

To find the z-score:
Convert 98% to a decimal: 0.98
Subtract from 1: 1-0.98 = 0.02
Divide by 2: 0.02/2 = 0.01
Subtract from 1: 1-0.01 = 0.99
Using a z-table (http://www.z-table.com) we see that this value is closest to a z-score of 2.33.
Using the z-score, our standard deviation (9) and our margin of error (3), we have:
X-y = 2
5x+3y =18
let do some plug and play
x-y = 2
x = 2+y
now we got an answer for x lets plug that in the other equation
5(2+y) + 3y = 18
10+5y + 3y = 18
10 + 8y = 18
8y = 8
y = 1
now lets find x
x = 2 +y
x = 2+ 1
x = 3.