we can solve this by first combining like terms: our like terms in this equation are d and plain numbers
so, this means that we can combine the d's with the d's and the plain numbers with the plain numbers
so,
7d + 12 - 4d - 3 = 0
3d+ 9 = 0
next, we have to get our plain numbers on one side of the equal sign, and our numbers with the d's on the other side of the equal sign: we do this by doing the opposite of what the number is doing on the side it is on, since the 9 is being subtracted from the left hand side, we will subtract it from both sides:
3d = -9
next, we want to get rid of the 3 next to the d
to do this, we would divide the 3 on both sides since it is being multiplied to the d on the left hand side:
d = -3
this is our final answer: d = -3
