Donna's penny bank can hold 1080 coins.
Explanation:
Step 1:
Assume the total number of coins that Donna's penny bank can hold is x.
So in the beginning, it was
full. So the number of coins were

After adding 240 pennies, it became
full. So the number of coins are

So it can be written as

Step 2:
So we need to determine the total number of coins that Donna's penny bank can hold i.e. the value of x.


Rounding this off, we get that Donna's penny bank can hold 1080 coins.