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First, distribute the -5 on the right side of the equation: -20d - 15 = -20d - 15.
Now, add 20d to both sides of the equation to isolate the variable: 0 = 0.
Since the equation simplifies to 0 = 0, this means that the variable "d" could take on any value and the equation would still be true. Therefore, this equation has infinitely many solutions.