Step 1 :Hall initially bought three bikes, each costing $30. So, the total cost for the bikes is \(30 \times 3 = 90\).
Step 2 :He then returned two bikes. Since each bike costs $30, he got back \(30 \times 2 = 60\).
Step 3 :Later, he bought a clock for $10.
Step 4 :So, the total change to Hall's funds is \(90 - 60 + 10 = 40\).
Step 5 :Final Answer: The total change to Hall's funds is \(\boxed{40}\).