Finding the Fourth Proportional to 139.10, 208.71 and 57.96

Step by Step Solution

1. Step 1: Write the proportion equation
   139.10 : 208.71 = 57.96 : x
2. Step 2: Convert to fraction form
   139.10/208.71 = 57.96/x
3. Step 3: Cross multiply
   139.10x = 208.71 × 57.96
4. Step 4: Simplify right side
   139.10x = 12,096.83
5. Step 5: Solve for x
   x = 12,096.83/139.10
6. Step 6: Final answer
   x = 86.97