Below is the answer to each part
Part 1. By the Pythagorean theorem:
x = √(9 ² + 15²)
x = 17,49
Part 2. By the Pythagorean theorem:
x = √(3² + 3²)
x = 4.24
Part 3
cos (45) = x / 16
x = 16cos (45) = 11.31
Part 4
Tan (60) = 12 / x
x = 12 / Tan (60)
x = 6.93
y = √(6,93²+ 12²)
y = 13,86