Three angles are acute angle and each measuring is 75° means
\(\angle\)A = \(\angle\)B = \(\angle\)C = 75°
(Acute angle is angle whose measuring is greater than 0 and less than 90.)
As we know that, Sum of all four angles of quadrilateral is 360o
\(\angle\)A + \(\angle\)B + \(\angle\)C + \(\angle\)D = 360°
75° + 75° + 75° + D = 360°
\(\angle\)D = 360° - (75° + 75° + 75°)
= 360° - 225°
= 135°
So, fourth angle of quadrilateral is 135°.
