Notice that the interest is defined as yearly, then, we have to take the time period as 2 years (since the money was saved 2 and a half years ago), then, using the equation of simple interest we have:
[tex]\begin{gathered} I=P\cdot n\cdot i \\ P=18,000 \\ n=2 \\ i=4.3\%=0.043 \\ \Rightarrow I=18,000(2\cdot0.043)=18000(0.086)=1548 \\ I=\$1548 \end{gathered}[/tex]Therefore, Tina has earned $1548
