( 1/4 ) X - 3 = ( 1/8 ) X + 5
( 1/4 ) X - ( 1/8 ) X = 5 + 3
( 2/8 ) X - ( 1/ 8 ) X = 8
( 1/8 ) X = 8
X = 8 : ( 1/8 )
X = 64
-----------------------------------
( 1/21 ) X + 84 = 85 + ( 1/7 ) X
( 1/7 ) X - ( 1/21 ) X = 84 - 85
( 3/21 ) X - ( 1/21 ) X = - 1
( 2/21 ) X = - 1
X = - 1 : ( 2/21 )
X = - 21/2
X = - 10,5