Tìm số x trong mỗi tỉ lệ thức sau:

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}$