As we know the first ounce cost $0.35, we can subtract that from $2.05.
Therefore, $2.05 - $0.35 = $1.70
We can then divide the remaining amount of money by $0.17 to find out how many more ounces the letter weighed.
$1.70/$0.17 = 10
Once we add the ounce before that costed $0.35 to the 10 ounces that we just calculated, we know that Amrit’s letter cost 11 ounces.