Sasa had some 20-cent and 50-cent coins. Let x be the total number of coins. Then, 7/8 x were 20-cent coins, and the rest, 1 - 7/8 = 1/8 x, were 50-cent coins. After Sasa spent $72.50 worth of 50-cent coins, which is equivalent to 72.50 / 0.50 = 145 50-cent coins, and 5/7 of the 20-cent coins, she had 2/7 x coins left. Find the total amount of money Sasa left.

Let $ x $ be the total number of coins Sasa initially had.

### Step 1: Breakdown of coins
- The number of 20-cent coins is given as $ \frac{7}{8}x $.
- The number of 50-cent coins is the remaining $ \frac{1}{8}x $.

### Step 2: Information about spent coins
- Sasa spent 145 of the 50-cent coins.
- She also spent $ \frac{5}{7} $ of the 20-cent coins.

### Step 3: Number of 50-cent coins left
The number of 50-cent coins left after spending 145 coins can be expressed as:
\[
\text{50-cent coins left} = \frac{1}{8}x - 145
\]

### Step 4: Number of 20-cent coins left
Sasa spent $ \frac{5}{7} $ of her 20-cent coins, so the remaining 20-cent coins are:
\[
\text{20-cent coins left} = \frac{2}{7} \times \frac{7}{8}x = \frac{2}{8}x = \frac{1}{4}x
\]

### Step 5: Total coins left
Sasa had $ \frac{2}{7}x $ coins left in total after spending. So, the sum of the 50-cent and 20-cent coins left must equal $ \frac{2}{7}x $:
\[
\frac{1}{4}x + \left( \frac{1}{8}x - 145 \right) = \frac{2}{7}x
\]

### Step 6: Solve for $ x $
Simplifying the equation:
\[
\frac{1}{4}x + \frac{1}{8}x - 145 = \frac{2}{7}x
\]
Convert all terms to have a denominator of 56:
\[
\frac{14}{56}x + \frac{7}{56}x - 145 = \frac{16}{56}x
\]
Combine like terms:
\[
\frac{21}{56}x - 145 = \frac{16}{56}x
\]
Subtract $ \frac{16}{56}x $ from both sides:
\[
\frac{5}{56}x = 145
\]
Multiply both sides by 56:
\[
5x = 8120
\]
Solve for $ x $:
\[
x = 1624
\]

### Step 7: Calculate the amount of money left
Now that we know $ x = 1624 $, we can calculate the remaining coins.

- The number of 20-cent coins left is $ \frac{1}{4} \times 1624 = 406 $.
- The number of 50-cent coins left is $ \frac{1}{8} \times 1624 - 145 = 203 - 145 = 58 $.

The total amount of money Sasa has left is:
\[
\text{Total money left} = 406 \times 0.20 + 58 \times 0.50 = 81.20 + 29.00 = 110.20
\]

Thus, the total amount of money Sasa has left is **$110.20**.

---

Do you want more details on the steps or have any other questions? 

Here are some related questions:
1. How would the problem change if Sasa spent 6/7 of the 20-cent coins instead?
2. What if Sasa had only $50 worth of 50-cent coins to spend?
3. Can you calculate how much Sasa would have if she spent all the 50-cent coins?
4. How does the proportion of 50-cent to 20-cent coins affect the total money left?
5. Can you determine how many total coins Sasa would have left if no 50-cent coins were spent?

**Tip:** When solving for the unknown, always ensure all variables and values are consistently expressed in the same units to simplify calculations.

This problem helps students solve an algebraic equation involving proportions. Sasa had a combination of 20-cent and 50-cent coins. After spending $72.50 worth of 50-cent coins and 5/7 of the 20-cent coins, she had a certain number of coins left. The solution demonstrates key algebraic concepts and linear equation solving, suitable for Grades 8-10.

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