Looks like all you can do is simplify this.
First take off the parenthesees.
8x - 3 + 7x - 12 + 4x
Then just combine the "like" terms.
19x - 15
You can think of that step like saying "Eight x's plus seven x's plus 4 x's equals nineteen x's. Just like 8 apples + 7 apples + 4 apples = 19 apples." And the ones that don't have an x beside them is just like saying, "Negative three nothings minus twelve nothings is negative fifteen nothings." Idk if that will make any sense to you but it makes sense to me.
ALSO IMPORTANT: Remember that if there is a minus outside the parenthesees you need to distribute it. For example, 5 - (3+4) is the same thing as 5 - 3 - 4.
