Finding the Fourth Proportional to 12,428.79, 18,643.18 and 8,521.35

Step by Step Solution

1. Step 1: Write the proportion equation
   12,428.79 : 18,643.18 = 8,521.35 : x
2. Step 2: Convert to fraction form
   12,428.79/18,643.18 = 8,521.35/x
3. Step 3: Cross multiply
   12,428.79x = 18,643.18 × 8,521.35
4. Step 4: Simplify right side
   12,428.79x = 158,865,061.89
5. Step 5: Solve for x
   x = 158,865,061.89/12,428.79
6. Step 6: Final answer
   x = 12,782.02