<Window x:Class="WPF_3_Grid_Layout.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="40" />
            <RowDefinition Height="*" />
            <RowDefinition Height="40" />
        </Grid.RowDefinitions>

        <Rectangle Grid.Row="0" Fill="Red" />
        <Grid Grid.Row="1">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="20*" />
                <ColumnDefinition Width="60*" />
                <ColumnDefinition Width="20*" />
            </Grid.ColumnDefinitions>

            <Rectangle Grid.Column="0" Fill="LightSeaGreen" />
            <Rectangle Grid.Column="1" Fill="SeaGreen" />
            <Rectangle Grid.Column="2" Fill="LightSeaGreen" />
        </Grid>
        <Rectangle Grid.Row="2" Fill="Green" />
    </Grid>
</Window>