What is -3x plus 5 plus 6 equals -15?

-3x + 5 + 6 = -15

Multiply by -1 (swap all signs): 3x - 5 - 6 = 15

Combine like terms on left side: 3x - 11 = 15

Add 11 to both sides: 3x = 26

Divide both sides by 3: x = 26/3 or 8.66...