Answer:
107 mm²
Explanation:
The formula of an area of a rectangle:

l - length
w - width
The area of a given shaded region is equal to the area of the whole rectangle, minus the area of the small rectangle.
Area of the whole rectangle:
l = 15mm, w = 9mm
A₁ = (15)(9) = 135 mm²
Area of the small rectangle:
l = 7mm, w = 4mm
A₂ = (7)(4) = 28 mm²
Area of the shaded region:
A = A₁ - A₂
A = 135 - 28 = 107 mm²