Part A: The error occurred in Step 2. Marcus incorrectly added the two fractions instead of multiplying them.
Part B:
Step 1: w over 0.14 = 4.2
Step 2: Multiply both sides by 0.14: 0.14w = 4.2 * 0.14
Step 3: Subtract 0.14 from both sides: 0.14w - 0.14 = 4.2 * 0.14 - 0.14
Step 4: Simplify: 0.14w = 4.06
Step 5: Divide both sides by 0.14: w = 4.06 / 0.14
Step 6: Simplify: w = 29