Finding the Fourth Proportional to 18,920.79, 28,405.89 and 12,708.50

Step by Step Solution

1. Step 1: Write the proportion equation
   18,920.79 : 28,405.89 = 12,708.50 : x
2. Step 2: Convert to fraction form
   18,920.79/28,405.89 = 12,708.50/x
3. Step 3: Cross multiply
   18,920.79x = 28,405.89 × 12,708.50
4. Step 4: Simplify right side
   18,920.79x = 360,996,111.04
5. Step 5: Solve for x
   x = 360,996,111.04/18,920.79
6. Step 6: Final answer
   x = 19,079.34