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x in (-oo:+oo)
200/12 = x/42 // - x/42
200/12-(x/42) = 0
50/3-1/42*x = 0 // - 50/3
-1/42*x = -50/3 // : -1/42
x = -50/3/(-1/42)
x = 700
x = 700
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