For number 1, you would have to subtract five on both sides to get 3x is greater than or equal to 15, then you would have to make the variable (x) on its own. So, you would divide 3x by three and 15 by three to get x=5.
I am not sure if you want me to do number two, but i will do it anyways, so 8(x+4) =-8, first you would have to multiply the eight into the parenthesis, so it would be 8x +32+-8 and then you would subtract 32 on both sides to get 8x=-40 you then divide -40 by 8 and you get x is greater than -5