Is - 3 a solution for the equation 2x + 4=2

No.

Let's solve the equation.

2x = 2-4

2x = - 2

2x/2 = - 2/2

x = - 1

The only solution is - 1

If you substitute - 3 to x

2 (-3) + 4 = 2

-6 + 4 = 2

-2 = 2 (so not true)

If we substitute - 1

2 (-1) + 4 = 2

-2 + 4 = 2

2 = 2