Answer:
B. y + z = x
Step-by-step explanation:
x is an exterior angle of the triangle.
y and z are the opposite angles opposite the exterior angle.
The exterior angle theorem of a triangle states that the measure of an exterior angle equals the measure of the sum of the two angles opposite the exterior angle.
Thus:
y + z = x
It's 5.
Because a constant is a number next to the variable.
9a+18=9
9a=-9
a=-1
