The way you tell whether a value is a solution or not is to try it in the equation.
A. -4*7 +2 = -26 ≠ 26 . . . . not a solution
B. -4*6 +2 = -22 ≠ 26 . . . . not a solution
C. -4*-7 +2 = 30 ≠ 26 . . . . not a solution
D. -4*-6 +2 = 26 = 26 . . . . this is your solution
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Of course, you can also solve the equation.
.. -4x +2 = 26
.. -4x = 24 . . . . . . subtract 2 (the term that doesn't contain x)
.. x = -6 . . . . . . . . .divide by -4 (the coefficient of x)