Answer: 41 degrees
so, we know that a triangle is 180 degrees. since we know that one angle is 80 degrees, we can subtract that from the equation. now, we are trying to find what X is so that we can find the angle. here is how i did it:
i rewrote it and removed the parentheses.
4x + 1 + 4x + 19 = 100
then, i collected like terms and calculated it.
8x + 20 = 100
then, i moved the constant to the right.
8x = 100 - 20
then, i simply calculated it.
8x = 10
solution: x = 10
so, we just insert X into the angle for A. that gets us 4(10) + 1 = angle A
40 + 1 = angle A, hence angle A = 41 degrees.