12 x = 48
x = 48 : 12
x = 4 → S = { 4 }
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5 x - 3 x = 10
2 x = 10
x = 10 : 2
x = 5 → S = { 5 }
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3 x - 17 = 16
3 x = 16 + 17
3 x = 33
x = 33 : 3 ⇒ x = 11 ⇔ S = { 11 }
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x + 180 = 200
x = 200 - 180
x = 20 ⇔ S = { 20 }