Answer:
Part 1: (2x + 15)° + (4x + 9)° = 90°
Part 2: x = 11
Part 3: First angle = 37°
Part 4: Second angle = 53°
Explanation:
Pt. 1: When two angles are complementary, they form a right angle and their sum is 90°
Thus, the equation we can use to find x is (2x + 15)° + (4x + 9)° = 90°
Pt. 2: Now we can simply solve for x:

Pts 3 & 4: Now that we've solved for x, we can plug in 11 for x for both angles to find their measures.
First angle: 2(11) + 15 = 22 + 15 = 37°
Second angle: 4(11) + 9 = 44 + 9 = 53°