The amount she earned doing the odd job is her principal. The principal can be calculated below
[tex]\begin{gathered} p=\frac{A}{(1+\frac{r}{n})^{nt}} \\ A=\text{accrued amount=100} \\ r=\text{rate}=10\text{ \%=}\frac{10}{100}=0.1 \\ t=6\text{ years} \\ n=4 \\ p=\frac{100}{(1+\frac{0.1}{4})^{24}} \\ p=\frac{100}{(1.025)^{24}} \\ p=\frac{100}{1.80872594958} \\ p=55.2875354186 \\ p=\text{ \$55.29} \end{gathered}[/tex]