16)
$(3-\sqrt[]{10})\sqrt[]{19+3\sqrt[]{40}}$
$=(3-\sqrt[]{10})\sqrt[]{19+2.3.\sqrt[]{10}}$
$=(3-\sqrt[]{10})\sqrt[]{(\sqrt[]{10})^2+2.3.\sqrt[]{10}+3^2}$
$=(3-\sqrt[]{10})\sqrt[]{(\sqrt[]{10}+3)^2}$
$=(3-\sqrt[]{10})|\sqrt[]{10}+3|$
$=(3-\sqrt[]{10})(3+\sqrt[]{10})$
$=3^2-(\sqrt[]{10})^2$
$=9-10$
$=-1$