private void toolStripButton1_Click(object sender, EventArgs e)
{
Task_3 newChild = new Task_3(); /*newChild.MdiParent = this;*/ newChild.Show();
newChild.Text = newChild.Text + " " + ++openDocuments;
}
/// <summary>
/// Відкриття третьої вправи
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void button3_Click(object sender, EventArgs e)
{
Task_3 task_3 = new Task_3();
task_3.Show();
}