215-(4.x+15)=128
(4.x+15)=215-128
(4.x+15)=87
4.x =87-15
4.x =72
x =72:4=18
215-(4.x+15)=128
(4.x+15)=215-128
4.x+15= 87
4.x=87-15
4.x=72
x=72:4 =18
Tìm x :
215 - ( 4x + 15 ) = 128
( 4x + 15 ) = 215 - 128
4x + 15 = 87
4x = 87 - 15
4x = 72
x = 72 : 4
x = 18