Answer
The tension in the short cord labeled $T$ must be $25~N$
Work Step by Step
We can see that the weight of $20~N$ hangs on a pulley with two parts of the red cord pulling up on the pulley. Therefore, the tension in the red cord is $10~N$
The short cord labeled $T$ pulls up on a pulley with two parts of the red cord pulling down on the pulley. There is also a weight of $5~N$ hanging down from the pulley.
Therefore, the tension in the short cord labeled $T$ must be $25~N$.
