Algebra is always a bit confusing when you first learn is as it's the first time letters come into maths, here is the mainthing you should remember:
you have to do the same thing to both sides of the equation!
Let's start with a much simpler example:
x - 5 = 9
to find out what x equals, we need to add 5 to both sides:
x - 5 + 5 = 9 + 5
as you can see the 5's on the left hand side cancel out, so we are left with:
x = 9 + 5 = 14.
Now lets move on to the harder question
0.5(6d+2)-4=10
there looks to be a lot of numbers here doing a lot of different things so go slowly and do each step at a time, first lets add 4 to both sides:
0.5(6d+2)=14
The next thing to deal with is the 1/2, here we need to times each side by 2, as 2x0.5=1, so:
6d+2=14x2
6d+2=28
Now take away 2 from both sides:
6d=28-2
6d=26
And finally divide both sides by 6, as 6/6=1, so:
d = 26/6
While this is the correct answer we can still simplify a bit further by dividing the top and the bottom of the fraction by 2:
d = 13/3