Question 254273
The last I knew parallelograms were not triangles so I moved your problem.
Is that a problem :)
Hints :
the angles of all parallelograms(including rectangles and squares) add up to 360  
The angles in  a parallelogram come in two equal pairs 
You already know one pair (two of them)  is each 75 degrees
So if the total is 360 and we have 150(2*75) what would th3e other two add up to?
And if we know what they add up to, we just have to divide that by 2 to get each angles of the pair