First you distribute the -2 :
5-2(x+2)=12 ---> 5-2x-4= 12
Next, you Combine Like Terms (Simplify):
5-2x-4=12 ---> -2x+1=12
After that, you subtract one from both sides:
-2x+1=12 ---> -2x=11
Finally, you divide both sides by -2:
-2x=11 ---> x= -5.5
Just remember PEMDAS ( Parenthesis, Exponents, Multiply/Divide, Add/Subtract). If you search it up on Google, you can find more details and examples :)