$$3 \times \frac{ 4 }{ 5 } \div (3 \times \frac{ 1 }{ 2 } +x) \div 21 \times \frac{ 3 }{ 7 } -1 \times \frac{ 3 }{ 8 } = \frac{ 5 }{ 8 }$$
$x = -\frac{711}{490} = -1\frac{221}{490} \approx -1.451020408$
