Please solve no.13 (i) from here only solve (i) please

The exchange rate (US$1 = S$x) means that for every S$ she will receive 1 US dollar. Therefore, one can write the equation:
[tex]\begin{gathered} y=x\begin{cases}x=S \\ y=US\end{cases} \\ y=2000\lbrack US\rbrack \end{gathered}[/tex]