First note that y cannot equal -7 or -1 as division by zero is undefined. So that if it comes up in our solution we know that it is not a real solution.
[(y+4)/(y+7)]+1=(y+3)/(y+1) make the left side have a common denominator
(y+4+y+7)/(y+7)=(y+3)/(y+1) combine like terms on left side
(2y+11)/(y+7)=(y+3)/(y+1) cross multiply
(2y+11)(y+1)=(y+3)(y+7) expand
2y^2+13y+11=y^2+10y+21 subtract y^2 from both sides
y^2+13y+11=10y+21 subtract 10y from both sides
y^2+3y+11=21 subtract 21 from both sides
y^2+3y-10=0 expand so factoring is easier
y^2-2y+5y-10=0 factor
y(y-2)+5(y-2)=0 which is equal to
(y+5)(y-2)=0
y=-5 or 2
