In the figure, yx−→− and yz−→− are tangents to circle a at points x and z, respectively.

mxz=140∘
mxsz=220∘

what is the measure of ∠xyz ?

We are given with
mXZ = 140∘
mXSZ = 220∘

and YX and YZ are tangents to circle A at X and Z.

According to the theorems on circles, the angles formed by the intersection of the two tangents is half the difference between of the measure of the arcs subtended by the tangents. So,
∠XYZ = (220 - 140) /2 = 40∘

The solution to the system of equations (-2,2)