Question

The sum of two numbers is 12. The first number, x, is twice the second number, y. Which system of equations could be used to find the two numbers?

Answer 1

x+y=12
y=2x

That is your equation because the first one shows that x plus y equals 12. The second equation is correct because it shows that two times x equals your y.

Leaving your two numbers to be x=4 y=8

Answer 2

The numbers are x and y, and their sum is 12. The word "sum" indicates addition; you will add x and y.

There's your first equation: x + y = 12

The first number, x, is twice the second number, y. In other words, x times 2 is y.

There's your second equation: 2x = y

The system of equations is: x + y = 12; 2x = y

If you needed to solve the system, you would first plug 2x for y into x + y = 12 and solve for x:

x + y = 12

x + 2x = 12

3x = 12

x = 4

Then you'd plug 4 for x into either equation to solve for y:

x + y = 12

4 + y = 12

y = 8

The solution to the system is (4, 8).