(20-19 3/4)+(17 3/4-17)+(2 1/2-17/24)

Compute each bracket:

• 20 − 19 3/4 = 20 − 79/4 = 1/4
• 17 3/4 − 17 = 3/4
• 2 1/2 − 17/24 = 5/2 − 17/24 = 60/24 − 17/24 = 43/24

Add them: 1/4 + 3/4 + 43/24 = 1 + 43/24 = 67/24 = 2 19/24

Final answer: 67/24 or 2 19/24.