Answer:
y + z = x
Step-by-step explanation:
Let's rename angle BAC to w. Now, we have four angles: w, x, y, and z. We know that w + y + z has to equal 180 degrees, because a triangle's three angels always adds up to 180 degrees. We also know that w + x equals 180 degrees, because they are on the same line. These two phrases are equal:
w + y + z = w + x
We can then cancel w on each side:
y + z = x
Hope this helps! :)