The coefficients in a chemical equation represent the molar ratio of the substances.
For example, if an equation says 2H2 + O2 ⇒ 2H2O, it means
2 moles of H2 + 1 mol of O2 ⇒ 2 moles of H2O.
Explanation:
most of the x-rays are absorbed in thermosphere of earth's atmosphere
The answer is -1. 2 subtraction signs next to each other for an addition sign