For 2 simple interest accounts, find earnings
Account A
$11.90 in 21 months is $0.57 per month
interest rate is 3.4%
then 3.4% is equal to $0.57
now 100% is equal to EARNINGS A
Multiply 100 x 0.57 / 3.4 = $16.76 dollars
Now finally add $16.76 + 11.90 =$ 28.66