The sum of two numbers is 20. One number is 3 times the other. Find the numbers.

x + 3x = 20

. . .

To solve this problem, let's break it down into steps:

Step 1: Define the variables
Let's assume that one of the numbers is x, and the other number is 3 times that number, so it will be 3x.

Step 2: Set up the equation
According to the problem, the sum of the two numbers is 20. So, we can write the equation as:
x + 3x = 20

Step 3: Simplify the equation
Combine like terms on the left side of the equation:
4x = 20

Step 4: Solve for x
To solve for x, we need to isolate it on one side of the equation. Divide both sides of the equation by 4:
x = 20 / 4
x = 5

Step 5: Find the other number
Now that we have found the value of x, we can find the other number by multiplying it by 3:
Other number = 3 * x
Other number = 3 * 5
Other number = 15

Step 6: Verify the solution
To verify our solution, we can substitute the values we found back into the original equation:
5 + 15 = 20

So, the two numbers are 5 and 15.