Câu 1:
6.(x+15)=294
x+15=49
x=34
Câu 2:
164:(5x-21)-1=8.5
164:(5x-21)-1=40
164:(5x-21)=41
5x-21=4
5x=25
x=5
294=6.(x+15)
=>x+15=294:6
=>x+15=49
=>x=49-15
=>x=34
164:(5.x-21)-1=8.5
=>164:(5.x-21)-1=40
=>164:(5.x-21)=40+1
=>164:(5.x-21)=41
=>5.x-21=164:41
=>5.x-21=4
=>5.x=21+4
=>5.x=25
=>x=25:5
=>x=5
294 = 6 . ( x + 15 )
6 . ( x + 15 ) = 294
x + 15 = 294 : 6
x + 15 = 49
x = 49 - 15
x = 34
164 : ( 5 .x - 21 ) - 1 = 8 . 5
164 : ( 5 .x - 21 ) - 1 = 40
164 : ( 5 .x - 21 ) = 40 + 1
164 : ( 5 . x - 21 ) = 41
( 5 . x - 21 ) = 164 : 41
( 5 . x - 21 ) = 4
5 . x = 4 + 21
5 . x = 25
x = 25 : 5
x = 5