Final answer:
The increase in DeShawn's investment account is $1833 and the total amount in his account at the end of last year is $9633.
Step-by-step explanation:
To calculate the increase in DeShawn's investment account, we need to find 23.5% of $7800. We can do this by multiplying 23.5% as a decimal (0.235) by $7800. So, the increase in DeShawn's investment account is:
$7800 * 0.235 = $1833
To find the total amount of money in DeShawn's account at the end of last year, we need to add the increase to the initial amount. So:
$7800 + $1833 = $9633