Answer:
Number of pennies Cary donated = 240
Explanation:
According to the question,
Pennies + Dimes = 800
number of pennies = 80% of 400 = 
 = 320
number of dimes = 400 - 32 = 80
then Cary donated some pennies.
Let us assume that Cary donated = x pennies
After donating some pennies, 50% of the remaining coins were pennies.
which can be written as;
320 - x = 

320 - x = 0.5 
 (400-x)
x = 240
So, number of pennies donated = 240