$$\frac{2}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{60}$$ $$=\frac{40}{60}+\frac{10}{60}+\frac{6}{60}+\frac{1}{60}$$ $$=\frac{40+10+6+1}{60}$$ $$=\frac{57}{60}$$ $$1-\frac{57}{60}=\frac{3}{60}=\frac{1}{20}$$