Step-by-step explanation:
[tex] \sqrt{7} + \sqrt{28} \div ( \sqrt{7 } - \sqrt{14} )[/tex]
[tex]\sqrt{7} + \sqrt{7 \times 4} \div ( \sqrt{7 } - \sqrt{7 \times 2} )[/tex]
[tex] \sqrt{7} (1 + 2) \div ( \sqrt{7} (1 - \sqrt{2} ))[/tex]
[tex] \dfrac{3}{1 - \sqrt{2} } [/tex]
