Finding the Fourth Proportional to 105.78, 158.76 and 86.76

Step by Step Solution

1. Step 1: Write the proportion equation
   105.78 : 158.76 = 86.76 : x
2. Step 2: Convert to fraction form
   105.78/158.76 = 86.76/x
3. Step 3: Cross multiply
   105.78x = 158.76 × 86.76
4. Step 4: Simplify right side
   105.78x = 13,774.02
5. Step 5: Solve for x
   x = 13,774.02/105.78
6. Step 6: Final answer
   x = 130.21