We can see that triangles ABC and AXY are congruent
This means that
Now, we know that BX=10, BY=8 and BA=AX+BX, hence AX=BA-BX, we have
now, since BA-BX=15-10, BA-BX=5, it yields,
Now, we need to isolate YC, this is given by
Since
we have that
hence, the answer is YC=4, which corresponds to A).