$a,$$-62. (27 -64)- 64. (62-27)$
$=-62 . 27 + 62.64 - 64.62 + 64.27$
$= 27$($64-2$)
$=27.2$
$=54$
$b,-37.65+ 37. (-23)+ (-37).12$
$=37(-65 + (-23) + (-12)$
$=37 .$ ($-100$)
$= -3700$
$c,-27.x + 52.x = -800 -15.x$
$-27x + 52x + 15x =-800$
$40x = -800$
$x = -20$
Vậy $x= -20$