Chapter 7 - Section 7.2 - Rational Exponents - Exercise Set - Page 425: 61

$y-y^{7/6}$

Using the Distributive Property and the laws of exponents, then, \begin{array}{l} y^{1/2}(y^{1/2}-y^{2/3}) \\\\= y^{\frac{1}{2}+\frac{1}{2}}-y^{\frac{1}{2}+\frac{2}{3}} \\\\= y^{\frac{2}{2}}-y^{\frac{3}{6}+\frac{4}{6}} \\\\= y-y^{7/6} .\end{array}