Answer:
<4 would be complementary to angle 3
Explanation:
I say this because you can see that other angles such as <2 and <5 are 90 degrees since they have a square. <1 and <6 is also 90 degrees even though they are two separate angles. Since <3 and <4 are adjacent to each other, it would only make sense that they are complementary angles (90 degrees angle) similar to the others!
-Hope this helps!