I really don't know what to do.
A step to step analysis on even one problem would be very nice... I have 35 problems like this and I really would like a very good example on how to do determine what to do on problems that are like this.
You need to isolate the variable. This one's fairly easy.
Just combine the constants on the left and ignore the subtraction of 0 from the right.
Last step is to divide each side of the equation by 12.
I must assume that in your second problem you meant to write:
Subtract 21 from both sides to isolate -7x on the left.
Finally, divide both sides of your equation by -7.