2) x=5 it is this because first u distribute the -2 to both the x and the +1 which gets you -2x-2=-12 then you add 2 (you add because you have to do the opposite of subtracting when you need to isolate the variable) to both sides to isolate 2x so you are left with 2x=10 then to get x all by itself you divide 2 to both sides so you are left with x=5
3) x=6 it is this because first you have to add 8 to both sides because you are doing the opposite to subtracting to get 7x alone so you get 7x=18+4x then you subtract 4x from both sides and get 3x=18 then divide 3 to both sides and you get x=6
4) a=2 it is this because first you distribute 3 into 6a and +12 which gets you 18a+36 , so you new equation will be 18a+36+4a=80 then you combine like terms so you combine 18a and 4a and you add them together to get 22a so your new equation is now 22a+36=80 then you subtract 36 from both sides to isolate 22a you are now left with 22a=44 then you divide 22 to both sides which leaves you with a=2
SORRY THIS IS A LOT! I TRIED TO EXPLAIN THE BEST I CAN! HOPE THIS HELPS :) have a nice day !