It will be used in high school.

2. Military angle measurement method, a system for measuring angles in dense locations. Divide the circumference into 6000 equal parts, and the central angle of each equal arc is called1angle. Secret numbers are written by drawing a short line between 100 and 10. For example, the secret number of 15 is written as? "0 15", 1370 is recorded as? " 1370"。 The conversion relationship between angular system and dense system is: 1 dense = 3 ′ 36 ″, 1 ≈ 16? Seven people.

3. Multiply 3NO2+H2O=2HNO3+NO by 2, then add 2NO+O2 and 2NO2 on both sides of the equation (2NO+O2 = 2NO2, so the original equation is still valid), and omit NO2 to get the result you want.