What is the the principal plus the interest for $300 borrowed at 6% for 1 year and $5,000 borrowed at 7.5% for 6 months?

$300 borrowed for 1 year at 6% incurs an interest of $300*0.06 = $18. The total amount including the principal and the interest is $318.

$5,000 borrowed at 7.5% for 6 months incurs an interest of $5000*0.075/2 = 187.5. The total amount including the principal and the interest is $5187.5

The amount in the first case is $318 and in the second it is $5187.5