Assuming the equation is (c+1)/(c-2) = 4/7, the answer is actually c = -5
(c+1)/(c-2) = 4/7
7*(c+1) = 4*(c-2) ... cross multiply
7c+7 = 4c-8
7c+7-7 = 4c-8-7 ... subtract 7 from both sides
7c = 4c-15
7c-4c = 4c-15-4c ... subtract 4c from both sides
3c = -15
3c/3 = -15/3 ... divide both sides by 3
c = -5
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Check:
(c+1)/(c-2) = 4/7
(-5+1)/(-5-2) = 4/7 ... replace every copy of 'c' with '-5'
(-4)/(-7) = 4/7
4/7 = 4/7 .. true equation; answer checks out
So the answer of c = -5 has been confirmed.