1) 
2)
is a right angle (perpendicular lines form right angles)
3)
is a right triangle (definition of a right triangle)
4)
and
are complementary (the acute angles of a right triangle are complementary)
Answer:
d = 7, 3
Step-by-step explanation:
First, you need to isolate the absolute value
-3|d - 5| = -6
divide both sides by -3:
|d - 5| = 2
break into 2 equations:
d - 5 = 2, d - 5 = -2
solve both equations and collect solutions:
d = 5 + 2, d = 5 - 2
d = 7, 3