X-21:85+7=22;x=?
x-9:74+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= $17 frac{1}{7}$