Whole numbers less than 20 are 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1. How to know if they are divisible by 3? Add the numbers, and if the sum is divisible by 3.
First you need to fix the equation in order to graph. x + y = 3 Subtract x from both sides. y = -1x + 3 Now graph. (Whenever there is a variable by itself there is always a 1 in front of it.) There is a site called desmos that can help↓