Answer:
x(y/2 + z)
Explanation:
There are two triangles here.
The small triangle which is bound by dotted lines has base = y and height = x
The height of the larger triangle is 2x and its base is y + z
Area of larger triangle = 1/2 · 2x · (y + z)
= x(y + z) = xy + xz
Area of smaller triangle = 1/2 · x · y = xy/2
Shaded region area = Area of larger triangle - area of smaller triangle
= xy + xz - xy/2
= xy/2 + xz
= x(y/2 + z)