a) $\frac{x}{26}=\frac{21}{39}$
$x\times 39=26\times 21$
x = 14
b) $4/5.2=x/\frac{2}{7}$
$frac{10}{13} = x/frac{2}{7}$
$x=frac{20}{91}$
c)$\frac{1.25}{0.1x}=\frac{1.35}{0.2}
$0.1x\times 1.35=1.25\times 0.2$
$x=\frac{50}{27}$
d*)$(3x-2)/\frac{7}{2}=\frac{4}{21}/\frac{1}{12}$
$(3x-2)times\frac{2}{7}=\frac{4}{21}times12$
$\frac{2(3x-2)}{7}=\frac{16}{7}$
2(3x - 2) = 16
$ x=\frac{10}{3}$