subscribe a read only property to the PropertyChanged event mvvm

In the view model there is a property that is dependent to another property value:

        private int _property;
        public int Property
        {
            get
            {
                return _property;
            }
            set
            {
                SetProperty(ref _property, value, () => Property);
            }
        }
        public int DependentProperty => Property + SomeLogic;

and the view:

<TextBlock Text="{Binding DependentProperty}" />

I want to update the view when the _property changes

I found :this question
that says you have to subscribe to the PropertyChanged event of Property, but I don't know how.

The DependentProperty is called computed property. In your case the INotifyPropertyChanged.PropertyChanged event is raised implicitly by calling the SetProperty method. All you have to do is to raise the event for the computed property explicitly.

Usually you already have an event invocator method implementation that is also used internally by the SetProperty method.
For example, if you use the .NET Community Toolkit you already inherit a protected virtual ObservableObject.OnPropertyChanged(propertyName: string):void method that you can call.

private int _property;
public int Property
{
  get => _property;
  set
  {
    // Implicitly raises the PropertyChanged event for this property
    // because SetProperty is calling OnPropertyChanged (event invocator method) internally.
    SetProperty(ref _property, value, () => Property);

    // Raise the PropertyChanged event explicitly for the computed property
    OnPropertyChanged(nameof(DependentProperty));
  }
}

public int DependentProperty => Property + SomeLogic;

Of course, if you want to avoid the explicit raising of the PropertyChanged event from every property that the computed property depends on, you can observe the required properties for changes:

private int _property;
public int Property
{
  get => _property;
  set => SetProperty(ref _property, value, () => Property);
}

public int DependentProperty => Property + SomeLogic;

public ViewModel()
{
  TrackDependentPropertySourceProperties();
}

private void TrackDependentPropertySourceProperties()
{
  this.PropertyChanged += OnDependentPropertySourcePropertiesChanged;
}

// Assume that DependentProperty depends on three other properties
// (use three to highlight the pattern)
private void OnDependentPropertySourcePropertiesChanged(object sender, PropertyChangedEventArgs e)
{
  switch (e.PropertyName)
  {
    case nameof(Property):
    case nameof(SomeOtherProperty):
    case nameof(AThirdProperty):
      OnPropertyChanged(nameof(DependentProperty));
  }
}

you need to implement INotifyPropertyChanged interface to model.

then implement

protected void OnPropertyChanged(string name)
{
     PropertyChangedEventHandler handler = PropertyChanged;
     if (handler != null)
     {
         handler(this, new PropertyChangedEventArgs(name));
     }
}

and when you set the property just call OnPropertyChanged(<ProperyName>).

Suggestion: Do not put business logic into the model itself.