Answer:
81 degrees
Step-by-step explanation:
A quadrilateral has four interior angles which sum up to 360 degrees.
As we are given that two angles are right angles which means the sum of two angles will be 180 degrees and the third angle is 99 degrees.
As we know that the four angles sum up to 360 degrees.
Let A,B,C and D denote the four angles,
Then
Sum of angles = 360
A+B+C+D=360
90+90+99+D=360
279+D=360
D=360-279
D= 81 degrees
So the fourth angle is 81 degrees ..
