since this is an isosceles triangle, this means that the two base angles are equal. therefore, 8y-7=73°, meaning that y = 10° (although we don't really need to know that since you're just supposed to find x).
the angles of a triangle add up to 180°, so we can add all the angles and set them equal to 180° to find x.
The slope of a perpendicular line is the "negative reciprocal" of the slope of the original line. so just switch the numbers and put the top number into a negative.
