$(X +9 ) + (X -8 ) + (X +7 ) + (X -6 ) + (X -5 ) + (X -4 ) = 63,6$
$⇒ X +9 +X -8 +X +7 +X -6 +X -5 +X -4 = 63,6$
$⇒ X × 6 + (9 -8 +7 -6 -5 -4) = 63,6$
$⇒ X × 6 -7 = 63,6$
$⇒ X × 6 = 70,6$
$⇒ X = 70,6 ÷ 6$
$⇒ X = \frac{353}{30}$
$Vậy$ $X = \frac{353}{30}$