Hallo,
B) -3x-15+9x-x = 5-x + 16
-3x+9x-x -15 = 5-x + 16
5x -15 = 5-x + 16
5x -15 = 5+ 16 -x
5x -15 = 21 -x -5x
-15 = 21 -6x |-21
-36= -6x| :(-6)
x=6
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7x-6x +5x-4=2-3x-4-x
6x -4 = -2-4x | +4
6x= 2 -4x |+4x
10x= 2 |:10
x=2/10= 1/5
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D) 2y +8-5y+4y = 28 - 3y + 14
2y -5y+4y +8 = 28 +14 -3y
y +8 = 42 -3y | -y
8= 42 -4y |-42
-34= -4y|: (-4)
34/4=y
y=17/2