Final answer:
Twenty times y being at most 100 can be written as the inequality 20y <= 100, which simplifies to y <= 5. The interval notation for this inequality is [-∞, 5].
Step-by-step explanation:
The equation 'Twenty times y is at most 100' can be written mathematically as 20y ≤ 100. To solve for 'y', we can divide both sides of the inequality by 20, which gives us y ≤ 5. This inequality describes all values of 'y' that are less than or equal to 5. When expressing this in interval notation, it is written as [-∞, 5]. This means that 'y' can be any number up to and including 5 but no greater.