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Which of the following system of equation is not equal to the system of equations is not equal to the system of equations shown below

Complete the statements about the system of linear equation respresented by the tables the equation respented the left table is

The fence around a quadrilateral-shaped pasture is 3a^2+15a+9 long. three sides of the fence have the following lengths: 5a, 10a-2, a^2-7. what is the length of the fourth side of the fence?