Sum all records from two different tables

Question

I have two different tables: Entrances and Exits. Each table has columns motive and value

I am using Typescript and Typeorm, and the Controller to list both is as follows:

class SaidaController {
  static listAll = async (req: Request, res: Response) => {
    const saidaRepository = getRepository(Saidas);
    const saidas = await saidaRepository.find({
      select: ["motivo", "valor"]
    });
    res.send(saidas);
  };
}

When I access the route /exits or /entrances, returns the following Json:

{
   "motivo": "MOTIVO Teste",
   "valor": "50"
}

How do I sum up all output records and all input records, and subtract the two?