The coefficient of x is not zero, so there is exactly one solution.
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6x +8 -2x(5) = 2(7) . . . . evaluate parentheses contents
6x +8 -10x = 14 . . . . . . . eliminate parentheses
-4x +8 = 14 . . . . . . . . . . collect x terms
-4x = 6 . . . . . . . . . . . . . . subtract 8
x = -6/4 = -3/2 . . . . . . . . divide by the coefficient of x