To determine how many marbles were originally in each bag, let's analyze the situation step-by-step:
- Each of the 5 bags originally contains \( m \) marbles.
- After adding 10 marbles to each bag, each bag contains \( m + 10 \) marbles.
- Therefore, the total number of marbles in all 5 bags after adding the marbles is \( 5(m + 10) \).
We need to set this expression equal to the total number of marbles provided, which is 80:
\[ 5(m + 10) = 80 \]
Now, looking at the answer choices:
A. \( 10 (m + 5) = 80 \)
B. \( 5 (m + 10) = 80 \)
C. \( 10m + 5 = 80 \)
D. \( 5m + 10 = 80 \)
The correct equation is:
B. \( 5(m + 10) = 80 \)