Find the missing number so that the equation has infinitely many solutions.2x+=2x–20

The equation you provided is: 2x + _ = 2x - 20

For an equation to have infinitely many solutions, both sides of the equation must be identical. This means that whatever we add to 2x on the left side must also result in 2x - 20 on the right side.

However, there is no number we can add to 2x that will result in 2x - 20 because the 2x on both sides will cancel each other out, leaving us with the equation: 0 = -20

This equation has no solution, so there is no number that can be added to the left side of the original equation to give it infinitely many solutions.