Answer
See below.
Work Step by Step
$a_1=3$
$a_2=\frac{2}{3}a_1=\frac{2}{3}3=2$
$a_3=\frac{2}{3}a_2=\frac{2}{3}2=\frac{4}{3}$
$a_4=\frac{2}{3}a_3=\frac{2}{3}\frac{4}{3}=\frac{8}{9}$
$a_4=\frac{2}{3}a_4=\frac{2}{3}\frac{8}{9}=\frac{16}{27}$
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