a) 420 + 65 . 4 = ( x + 175 ) : 5 + 30
680 = ( x + 175 ) : 5 + 30
( x + 175 ) : 5 = 680 - 30
( x + 175 ) : 5 = 650
x + 175 = 650 . 5
x + 175 = 3250
x = 3250 - 175
x = 3075
Những câu sau làm giống vậy
a.420 + 65 . 4 = ( x + 175 ) : 5 + 30
680 = ( x + 175 ) : 5 + 30
( x + 175 ) : 5 = 680 - 30
( x + 175 ) : 5 = 650
x + 175 = 650 x 5
x + 175 = 3250
x = 3250 - 175
x = 3075
[ ( x + 32 ) - 17 ] . 2 = 42
[ ( x + 32 ) - 17 ] = 42 : 2
( x + 32 ) - 17 = 21
( x + 32 ) = 21 + 17
x + 32 = 38
x = 38 - 32
x = 6
b. ( 32 . 15 ) : 2 = ( x + 70) : 14 - 40
240 = ( x + 70 ) : 14 - 40
( x + 70 ) : 14 = 240 + 40
( x + 70 ) : 14 = 280
( x + 70 ) = 280 . 14
x + 70 = 3820
x = 3920 - 70
x = 3850