Answer:
He would have to invest $80,412.
Explanation:
Compound interest:
The compound interest formula is given by:

Where A(t) is the amount of money after t years, P is the principal(the initial sum of money), r is the interest rate(as a decimal value), n is the number of times that interest is compounded per year and t is the time in years for which the money is invested or borrowed.
Assuming an interest rate of 3,43% compounded quarterly.
This means that

How much would he have to invest to have $148,700 after 18 years?
This is P for which
. So




He would have to invest $80,412.