Answer:
3c + 8d - cd 
Explanation:
Now we have to,
→ Simplify the given expression. 
The expression is,
→ 4cd - 5cd + 3c + 8d
Let's simplify the expression,
→ 4cd - 5cd + 3c + 8d
→ 3c + 8d + 4cd - 5cd 
→ (3c) + (8d) + (4cd - 5cd)
→ 3c + 8d + (-cd) 
→ 3c + 8d - cd 
Hence, answer is 3c + 8d - cd.