Compound Inequalities, Union - Definition & Examples

Shia and Leslie are at a carnival when they come across a guessing game. A big jar is filled to the top with M&M's, and the goal is to guess how many M&M's are in the jar. $\\$ Shia takes one look and guesses that there are at least 1200, but no more than 1500. Leslie's guess is some number between 900 and 1300, inclusive. How would you express the union of their guesses in interval notation?