What is y^2-7y+6=0 and you have to solve for y

Y^2 - 7y + 6 = 0
(y - 1)(y - 6) = 0

y - 1 = 0
y = 1

y - 6 = 0
y = 6

so y = 1 or y = 6

There are several different methods you could use to solve y^2=7y+6=0.  One is to factor and then to set each factor = 0 and solve for y in each case:

(y-6)(y-1)=0 yields the equations y-6=0 and y-1=0.  Solve these two equations for the two roots.

Another approach would be to apply the quadratic formula.  Here a=1, b=-7 and c=6.