Formulate but do not solve the problem.

Kelly Fisher invested a total of $20,000 in two municipal bonds that have yields of 8% and 9% interest per year, respectively. If the interest Kelly receives from the bonds in a year is $1680, how much did she invest in each bond? (Let x and y denote the amount, in dollars, invested at 8% and 9%, respectively.)
____ = 20,000
_____ = 1680

Let x be the amount invested at 8% (denoted as x).

Therefore, the amount invested at 9% would be 20,000 - x.

The interest earned from the 8% investment would be x * 8% = 0.08x dollars.

The interest earned from the 9% investment would be (20,000 - x) * 9% = 0.09(20,000 - x) dollars.

The total interest earned is given as $1680, so the equation can be written as:

0.08x + 0.09(20,000 - x) = 1680

Now you can solve this equation to find the values of x and (20,000 - x), which represent the amounts invested in each bond.

do this just like your previous exercise.