a)
[tex] \sqrt{9 \sqrt{ 16} } = \sqrt{9 \times 4} = \sqrt{36} = 6[/tex]
b)
[tex] \sqrt{16} + \sqrt{36} = 4 + 6 = 10[/tex]
c)
[tex] \sqrt{ \frac{98}{128} } = \sqrt{ \frac{49}{64} } = \frac{7}{8} [/tex]