The sum of three numbers is 20. The first number is the sum of the second and the third. The third number is three times the first. Find the numbers.

The answer is - 20, 10, and 30.

Step-by-step explanation:

x + y + z = 20

x = y + z

z = 3x

substitute z = 3x

x = y + 3z

-2x = y

substitute z = 3x and y = - 2x

x + (-2x) + 3x = 20

2x = 20

x = 10

z = 3x = 30

y = - 2x = - 20

Now let's check the answer.

x + y + z = 10 - 20 + 30 = 20