a) x : [( 1800 + 600 ) : 30] = 560 : (315 - 35 )
=> x : ( 2400 : 30 ) = 560 : 280
=> x : 80 = 2
=> x = 2 . 80
=> x = 160
Vậy x = 160
b) [( 250 - 25 ) : 15 ] : x = ( 450 - 60 ) : 130
=> ( 225 : 15 ) : x = 390 : 130
=> 15 : x = 3
=> x = 15 : 3
=> x = 5
Vậy x = 5