At first, the ratio of Weijie's savings to Lihua's savings was 5 : 4.
After each of them spent $40, the ratio of Weijie's savings to Lihua's savings became 13 : 10. What was Lihua's savings at first? Ans: $ ___

1. Identify the constant difference and find the difference in units for both ratios

Since both Weijie and Lihua spent the same amount ($40), the difference between their savings remains constant.
Initial ratio difference = $5 - 4 = 1$ unit
Final ratio difference = $13 - 10 = 3$ units

2. Make the difference in units the same for both ratios

Multiply the initial ratio by 3 to match the final difference of 3 units:
Initial ratio = $(5 \times 3) : (4 \times 3) = 15 : 12$

3. Find the value of 1 unit

Decrease in units for Lihua = $12 - 10 = 2$ units
$2 \text{ units} = \char36{}40$
$1 \text{ unit} = \char36{}40 \div 2 = \char36{}20$

4. Calculate Lihua's savings at first

Lihua's initial savings = $12 \text{ units} = 12 \times \char36{}20 = \char36{}240$