$$\sqrt{0.16\cdot25}-\sqrt{1.36}=\sqrt{\frac{16}{100}\cdot25}-\sqrt{\frac{136}{100}}=\sqrt{\frac{4}{100}\cdot100}-\sqrt{\frac{4\cdot34}{100}}=\sqrt{4}-\sqrt{\frac{4}{100}\cdot34}=2-\frac{2}{10}\sqrt{34}=2-\frac{1}{5}\sqrt{34}$$
Ответ: $$2-\frac{1}{5}\sqrt{34}$$