Finding the Fourth Proportional to 12,139.05, 16,749.93 and 7,665.21

Step by Step Solution

1. Step 1: Write the proportion equation
   12,139.05 : 16,749.93 = 7,665.21 : x
2. Step 2: Convert to fraction form
   12,139.05/16,749.93 = 7,665.21/x
3. Step 3: Cross multiply
   12,139.05x = 16,749.93 × 7,665.21
4. Step 4: Simplify right side
   12,139.05x = 128,391,730.94
5. Step 5: Solve for x
   x = 128,391,730.94/12,139.05
6. Step 6: Final answer
   x = 10,576.75