Steps of construction of △DEF:
Step 1:
Draw the base line EF of the length 7.5 cm.
Step 2:
Measure the angle E with your protractor. Make a mark at 75 degrees and draw a line from E passing through the mark.
Step 3:
Measure the angle F with your protractor. Make a mark at 55 degrees and draw a line from F passing through the mark.
Step 4:
Name the point of intersection of these two lines as D and the △DEF is complete, as shown below.
Now, from the above construction the measure of ∠D is 50∘.