$\boxed{300,000 + 40,000 + 5,000 + 600 + 70 + 8}$Step-by-step explanation:The expanded form of 345,678 is:300,000 + 40,000 + 5,000 + 600 + 70 + 8Let's break it down by place value:- 3 is in the hundred thousands place (300,000)- 4 is in the tens thousands place (40,000)- 5 is in the thousands place (5,000)- 6 is in the hundreds place (600)- 7 is in the tens place (70)- 8 is in the ones place (8)So, the expanded form is: 300,000 + 40,000 + 5,000 + 600 + 70 + 8 = 345,678 ✅