Chapter 7 - Section 7.4 - Adding, Subtracting, and Multiplying Radical Expressions - Exercise Set - Page 438: 9

$5b\sqrt[]{b}$

Using the properties of radicals, then, \begin{array}{l} \sqrt[]{9b^3}-\sqrt[]{25b^3}+\sqrt[]{49b^3} \\= \sqrt[]{9b^2\cdot b}-\sqrt[]{25b^2\cdot b}+\sqrt[]{49b^2\cdot b} \\= 3b\sqrt[]{b}-5b\sqrt[]{b}+7b\sqrt[]{b} \\= 5b\sqrt[]{b} .\end{array}