Answer is D
When there is no mistake in a and b, the sum of roots ($-\frac{b}{a}$) must be correct.
When there is no mistake in a and c, product of the roots ($\frac{c}{a}$) must be correct.
Therefore sum of roots = 6+2 = 8 and product of roots -7*-1 = 7
So the correct equation is $x^{2}-8x+7=0$
(x-7) (x-1). The roots are 7, 1