For r+t/r-t to be positive,
-> Option 1: r is postive and > t
-> Option 2: r is negative and < t
The fact that t is greater than zero (St: 1) doesn't do much help, since it is subtracted in denominator.
The fact that r is greater than zero (St: 2) removes option 2 and assures r>t
took more than 2 minutes though