Explanation: To solve for <em>d</em> in this problem, the first thing we want to do is subtract 2 from both sides of the equation in order to get the <em>d</em> term by itself.
On the left side, 2 - 2 cancels and here is the tricky part. Make sure you understand that we're left with a -7d on the left side of the equation. Students often forget to bring down the negative.
On the right side we have 15 - 2 which simplifies to 13.
Now to get <em>d</em> by itself we just divide both sides of the equation by -7.
The -7's cancel so we have 13 divided by -7 which is about -1.85714285714.
So <em>d = -1.85714285714</em>.
