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x in (-oo:+oo)
3/8 = x/1200 // - x/1200
3/8-(x/1200) = 0
3/8-1/1200*x = 0 // - 3/8
-1/1200*x = -3/8 // : -1/1200
x = -3/8/(-1/1200)
x = 450
x = 450
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