First we'll find x, then we'll find Angle B (by substituting in x), then we'll find Angle C (bc Angle B and C are supplementary--that us, they add up to 180°)
10x-19 = 7x+23 subtract 7x
3x-19 = 23 add 19
3x = 42 divide by 3
x = 14
Angle B is 10x-19, and if x=14, then its 10(14)-19
Assuming you know how to simplify this, I will not show the steps but can add them later on upon request
Lets use the quadratic formula now
Multiply the numbers 2 * 1 = 2
Moving on, I will do the second part excluding the extra details that I had shown previously as from the first portion of the quadratic you can easily see what to do for the second part.