What does the x mean in the equation 3x-7=5x+13

Solution 

1) Subtract 3x from both sides

−7=5x+13−3x

2) Simplify 5x+13−3x to 2x+13

−7=2x+13

3) Subtract 13 from both sides

−7−13=2x

4) Simplify −7−13 to −20

−20=2x

5) Divide both sides by 2 

 -  = x

6) Simplify -  to 10

−10=x 

THE ANSWER IS -10 = x 

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CHECK YOUR ANSWER

3x−7=5x+13

1) Let x=−10

3×−10−7=5×−10+13

2) Simplify 3×−10 to −30

−30−7=5×−10+13

3) Simplify 5×−10 to −50

−30−7=−50+13

4) Simplify −30−7 to −37
−37=−50+13

5) Simplify −50+13 to −37

−37=−37

THE ANSWER IS CORRECT 

Logical equivalent of the give question is its contrapositive