Basically, to solve all of those problems you put all the variables on one side and the integers on the other side then solving for the variable.
I'll solve a few to demonstrate this idea.
3. 8r + 4 = 10 + 2r
In this case r is our variable.
We want to move all the r's to the same side.
Subtract 2r from both sides
8r + 4 -2r = 10 + 2r - 2r
6r + 4 = 10
Subtract 4 from both sides
6r + 4 - 4 = 10 - 4
6r = 6
Solve for r by dividing both sides by 6.
6r/6 = 6/6
r = 1
2. 28 - 0.3y = 0.7y - 12
y is the variable in this equation
It will be easier to move all the y's to the right side in this scenario.
Add 0.3y to both sides to do this.
28 - 0.3y + 0.3y = 0.7y -12 + 0.3y
28 = 0.7y + 0.3 y -12
28 = 1y -12
28 = y - 12
Move 12 to the left side by adding 12 to both sides.
28 + 12 = y - 12 + 12
40 = y
y = 40
You can use the same steps to solve the rest.
If you have any questions on any particular one that you don't know how to do, feel free to comment below and I will walk you through it. Otherwise, I know you will be able to solve the rest!
