Question

is the equation 8 + 4= -5 + 7 true false or open and why

Answer 1

This is false, because the equation is then 12=2, which is incorrect.

Hope this helps!

~ThePirc

Answer 2

1. Solve
8 + 4 = -5 + 7
12 = 2

Obviously 12 doesn't equal 2 so the equation is false. Here are the definitions:
True: The equation is true. 
Example: 2 =2

False: The equation is false or not true. 
Example: -2 = 2

Open: The equation is true or false depending on what the variable is. 
Example: 2x = 2