Finding the Fourth Proportional to 105.59, 158.18 and 80.91

Step by Step Solution

1. Step 1: Write the proportion equation
   105.59 : 158.18 = 80.91 : x
2. Step 2: Convert to fraction form
   105.59/158.18 = 80.91/x
3. Step 3: Cross multiply
   105.59x = 158.18 × 80.91
4. Step 4: Simplify right side
   105.59x = 12,797.94
5. Step 5: Solve for x
   x = 12,797.94/105.59
6. Step 6: Final answer
   x = 121.20