Question

Difficulty: EasySystems of Linear Equations

Consider the system of equations below.

x=2yx = 2y
3xy=103x - y = 10

If (x,y)(x, y) is the solution to the system of equations above, what is the value of xx?

Answer: 4

Answer

The value of xx is 44.
The system of equations can be solved by substituting x=2yx = 2y from the first equation into the second equation, which gives 3(2y)y=103(2y) - y = 10. Simplifying this equation yields 6yy=106y - y = 10, or 5y=105y = 10. Dividing by 55 gives y=2y = 2. Substituting y=2y = 2 back into the first equation yields x=2(2)=4x = 2(2) = 4. Therefore, the value of xx is 44.

Step-by-Step Solution

1
Substitute the expression for xx from the first equation into the second equation.
3(2y)y=103(2y) - y = 10
Since the first equation gives xx in terms of yy, substituting it into the second equation reduces the system to a single linear equation in one variable.
2
Solve the resulting equation for yy.
y=2y = 2
Simplifying 3(2y)y=103(2y) - y = 10 yields 6yy=106y - y = 10, which simplifies further to 5y=105y = 10. Dividing both sides by 55 gives y=2y = 2.
3
Substitute the value of yy back into the first equation to solve for xx.
x=4x = 4
Using x=2yx = 2y and substituting y=2y = 2 gives x=2(2)=4x = 2(2) = 4.

Key Concept

Solving systems of linear equations using the substitution method.
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