If these are whole numbers, then st=13 means that either s=1 and t=13 or s=13 and t=1.
rs = 16 means that s is a divisor of 2, and s=13 won't work, so s must be 1 and t=13.
Since s=1 and rs=16, r = 16/s = 16
So rt = (16)(13) = 208
If these are not whole numbers, then the other answers have shown you that rt=208/s² can be any positive number. (If complex numbers are allowed, then rt can be any nonzero number, real or complex.)
