Finding the Fourth Proportional to 139.22, 208.69 and 57.98

Step by Step Solution

1. Step 1: Write the proportion equation
   139.22 : 208.69 = 57.98 : x
2. Step 2: Convert to fraction form
   139.22/208.69 = 57.98/x
3. Step 3: Cross multiply
   139.22x = 208.69 × 57.98
4. Step 4: Simplify right side
   139.22x = 12,098.51
5. Step 5: Solve for x
   x = 12,098.51/139.22
6. Step 6: Final answer
   x = 86.91