Hallo,
a) 101 + 3x = 1 - 17x | +17x
101 +20x = 1 |- 101
20x= -100|: 20
x= -5
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b) 3d + 47 = 11 - d |+d
4d +47= 11| -47
4d= -36 |:4
d=-9
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c) -r - 20 = -5r -72 ||+72
-r +52= -5r | +r
52= -4r |: (-4)
r= -13