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q in (-oo:+oo)
13 = (1900-(2*q))/42 // - (1900-(2*q))/42
13-((1900-(2*q))/42) = 0
13-((1900-2*q)/42) = 0
(-1*(1900-2*q))/42+13 = 0
(-1*(1900-2*q))/42+(13*42)/42 = 0
13*42-1*(1900-2*q) = 0
2*q-1354 = 0
(2*q-1354)/42 = 0
(2*q-1354)/42 = 0 // * 42
2*q-1354 = 0
2*q-1354 = 0 // + 1354
2*q = 1354 // : 2
q = 1354/2
q = 677
q = 677
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