Math Problem Statement

Write a system of linear equations based on the angles of a trapezoid and solve for x and y.

Solution

To solve this problem, we are working with a trapezoid, and the four labeled angles are based on the variables xx and yy. Since these angles make up the interior angles of a quadrilateral, we know that the sum of the interior angles of any quadrilateral is 360 degrees.

The four angles provided are:

  1. 2y2y^\circ (upper-left)
  2. 4x4x^\circ (upper-right)
  3. (2x+12)(2x + 12)^\circ (lower-left)
  4. (y+6)(y + 6)^\circ (lower-right)

Step 1: Set up the equation for the sum of angles

We know the sum of these angles is 360 degrees, so we can write:

2y+4x+(2x+12)+(y+6)=3602y + 4x + (2x + 12) + (y + 6) = 360

Step 2: Combine like terms

Combine all the terms involving xx and yy:

(4x+2x)+(2y+y)+12+6=360(4x + 2x) + (2y + y) + 12 + 6 = 360

This simplifies to:

6x+3y+18=3606x + 3y + 18 = 360

Step 3: Subtract 18 from both sides

6x+3y=3426x + 3y = 342

Step 4: Simplify further by dividing by 3

2x+y=1142x + y = 114

This is Equation 1.

Step 5: Identify a second equation

Since the two angles on the same side of a trapezoid are supplementary (i.e., they sum to 180 degrees), we can form another equation based on this fact. Let’s use the two angles on the left side, 2y2y^\circ and (2x+12)(2x + 12)^\circ:

2y+(2x+12)=1802y + (2x + 12) = 180

Step 6: Simplify the second equation

2y+2x+12=1802y + 2x + 12 = 180

Subtract 12 from both sides:

2y+2x=1682y + 2x = 168

Divide through by 2:

y+x=84y + x = 84

This is Equation 2.

Step 7: Solve the system of equations

Now we solve the system of equations:

  1. 2x+y=1142x + y = 114
  2. x+y=84x + y = 84

Subtract Equation 2 from Equation 1:

(2x+y)(x+y)=11484(2x + y) - (x + y) = 114 - 84

Simplifying:

x=30x = 30

Now substitute x=30x = 30 into Equation 2:

30+y=8430 + y = 84

Solving for yy:

y=54y = 54

Final Answer:

x=30,y=54x = 30, \quad y = 54

Would you like more details or have any questions?

Follow-up Questions:

  1. How do you check that the sum of the angles is correct?
  2. Can you generalize this process for any quadrilateral?
  3. What would the equations look like if the angles were different?
  4. How would the process change if this were a different type of polygon?
  5. What happens if two angles are supplementary but non-adjacent?

Tip:

When dealing with angle sums in polygons, remember that the sum of the interior angles of an nn-sided polygon is (n2)×180(n-2) \times 180^\circ.

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Math Problem Analysis

Mathematical Concepts

Algebra
Geometry
Systems of Linear Equations
Angle Sum of a Quadrilateral
Supplementary Angles

Formulas

Sum of interior angles of a quadrilateral: 360°
Supplementary angles sum: 180°
Equation 1: 2x + y = 114
Equation 2: x + y = 84

Theorems

Sum of Interior Angles Theorem
Supplementary Angles Theorem

Suitable Grade Level

Grades 8-10