This question is based on the definition of feasible region. Let us take one example and try to understand feasible region using that.
Let the constraints for a linear problem be
x + y ≤ 4
x ≥ 0 and y ≥ 0
The region common to all these three regions are the shaded part in the figure given below
If we take any point from the shaded region, it will satisfy all the three inequalities or constraints. We call this shaded region the feasible region for this linear programming problem