Who solved the problem incorrectly, and where was the first mistake made?

Answer:
B
Step-by-step explanation:
20 × 30 = 600
30 × 6 = 180
5 × 6 = 30
but 20 × 5 doesn't equal 10
Answer: B
explanation: mariah was doing it right until she multiplied 20x5. she put 10, which is wrong. it’s 100