３\(\sqrt{\quad}\)２８＋\(\sqrt{\quad}\)６３－４\(\sqrt{\quad}\)７
＝３\(\sqrt{\quad}\)（４×７）＋\(\sqrt{\quad}\)（９×７）－４\(\sqrt{\quad}\)７
＝３×２\(\sqrt{\quad}\)７＋３\(\sqrt{\quad}\)７－４\(\sqrt{\quad}\)７
＝（６＋３－４）\(\sqrt{\quad}\)７
＝５\(\sqrt{\quad}\)７……（答）