The rule of the compound interest is
A is the new amount
P is the initial amount
r is the rate in decimal
n is the number of the periods per year
t is the number of years
Since the rate is 7% compounded semi-annual, then
r = 7/100 = 0.07
n = 2
Since the amount after 3 years will be $11 000, then
A = 11 000
t = 3
Substitute them in the rule above to find P
Divide both sides by (1.035)^6 to find P
Round it to the nearest cent (2 decimal places)
P = $8948.51
The amount invested was $8948.51