Because the 2 sides of the triangle are the same, they are both 21, the two bottom angles would also be the same.
The 3 inside angles of a triangle must equal 180 degrees.
The top angle is given as 38, so the remaining two angles must equal 180 - 38 = 142 degrees.
Since the 2 bottom angles would be the same, divide 142 by 2 to get x.
X = 142 / 2 = 71 degrees.
His mistake was adding 12+2 when he was supposed to subtract.
General Idea:
(i) Assign variable for the unknown that we need to find
(ii) Sketch a diagram to help us visualize the problem
(iii) Write the mathematical equation representing the description given.
(iv) Solve the equation by substitution method. Solving means finding the values of the variables which will make both the equation TRUE
Applying the concept:
Given: x represents the length of the pen and y represents the area of the doghouse
<u>Statement 1: </u>"The pen is 3 feet wider than it is long"

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<u>Statement 2: "He also built a doghouse to put in the pen which has a perimeter that is equal to the area of its base"</u>

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<u>Statement 3: "After putting the doghouse in the pen, he calculates that the dog will have 178 square feet of space to run around inside the pen."</u>

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<u>Statement 4: "The perimeter of the pen is 3 times greater than the perimeter of the doghouse."</u>

Conclusion:
The systems of equations that can be used to determine the length and width of the pen and the area of the doghouse is given in Option B.

Step-by-step explanation:
Name the total of pens purchased as x and the pencils as y... Make two equations and solve them. I also search for the pencils purchased in addition
Well sir according to my calculations if you have a 3 and than you add 3 to the 3 you already have then you would end up with the exact answer of number 6