$\frac{ 21 }{ 8 } \times 1 \frac{ 3 }{ 4 }\div3 \frac{ 1 }{ 5 }$
Convert the mixed number to an improper fraction$\frac{ 21 }{ 8 } \times \frac{ 7 }{ 4 }\div3 \frac{ 1 }{ 5 }$
Convert the mixed number to an improper fraction$\frac{ 21 }{ 8 } \times \frac{ 7 }{ 4 }\div\frac{ 16 }{ 5 }$
To divide by a fraction, multiply by the reciprocal of that fraction$\frac{ 21 }{ 8 } \times \frac{ 7 }{ 4 } \times \frac{ 5 }{ 16 }$
Multiply the fractions$\begin{align*}&\frac{ 735 }{ 512 } \\&\begin{array} { l }1 \frac{ 223 }{ 512 },& \approx1.43555\end{array}\end{align*}$