X-21:8*5+7=22;x=? x-9:7*4+8=20;x=?

$x- \frac{21}{8} *5+7=22$
$\frac{8x-49}{8} = \frac{22}{1}$ ⇒ $(8x-49)*1=8*22$
$\frac{8x-49}{8x} = \frac{8*22}{8x}$
$\frac{8*22}{8x} = \frac{22}{x}$
$\frac{8x-49}{8x} = \frac{22}{x}$
$1- \frac{49}{8x} = \frac{22}{x}$
$- \frac{225}{8x} =-1$
$\frac{8x-225}{8x} =0$
8x=225
x= $\frac{225}{8}$
x= $28 \frac{1}{8}$

$x- \frac{9}{7} *4+8=20$
$\frac{7x+20}{7} = \frac{20}{1}$ ⇒ $(7x+20)*1=7*20$
$\frac{(7x+20)*1}{7x}$ = $\frac{7*20}{7x}$
$\frac{7x+20}{7x} = \frac{7*20}{7x}$
$\frac{7*20}{7x} = \frac{20}{x}$
$\frac{7x+20}{7x} = \frac{20}{x}$
$\frac{20}{7x} +1= \frac{20}{x}$
$-\frac{120}{7x} =-1$
$\frac{7x-120}{7x} =0$
7x=120
$x= \frac{120}{7}$
x= $17 \frac{1}{7}$