To find angle D you need to first find the last angle of the triangle
A triangles interior angles add to 180
so we know that two angles equal 38
so 38+38=76
So to find the last angle subtract 76 from 180
180-76=104
So angle D in a part of a straight line...
A straight line is also equal to 180
so since we know that other angle is 104
We do 180-104 which is 76
Angle D = 76