Hey there!
12x + 15 = 15x
SUBTRACT 15x to BOTH SUDES
12x + 15 - 15x = 15x - 15x
SIMPLIFY IT!
NEW EQUATION: -3x + 15 = 0
SUBTRACT 15 to BOTH SIDES
-3x + 15 - 15 = 0 - 15
CANCEL outs 15 - 15 because it give you 0
KEEP: 0 - 15 because it help solve for the x-value
NEW EQUATION: -3x = 0 - 15
SIMPLIFY IT!
-3x = -15
DIVIDE -3 to BOTH SIDES
-3x/-3 = -15/-3
CANCEL out: -3/-3 because it give you 0
KEEP: -15/-3 because it gives you the x-value
NEW EQUATION: x = -15/-3
SIMPLIFY IT!
x = 5
Therefore, your answer is: x = 5
Good luck on your assignment and enjoy your day!
~Amphitrite1040:)