Answer:
1 square unit
Step-by-step explanation:
Area of the shaded region
= Area of the triangle with base 3 units and height 1 unit - Area of triangle with base 1 unit and height 1 unit.
= 1/2 *3*1 - 1/2 *1*1
= 1.5 - 0.5
= 1 square unit
