The key to solving equations is doing the inverse, or opposite, function/process. For example, you subtract when d + 1 = 2: d + 1 = 2 (d + 1) -1 = (2) - 1 d = 1
In the same way, you add values when you have a negative: 5.5 = -2 + d = d - 2 5.5 = d - 2 (5.5) + 2 = (d - 2) + 2 7.5 = d
Now if instead of adding 2, you subtract 2, the problem becomes: 5.5 = d - 2 (5.5) - 2 = (d - 2) - 2 3.5 = d - 4
This doesn't solve your problem, it just makes the value needed to be canceled out larger.
Thus d = 7.5 and you will add because the value is negative.
Since 2 is negative, you would want to add the 2 to each side. You want to cancel out the number so you leave d by itself, so it'll always be opposite of whatever the sign is. 5.5= -2 + d +2 +2 7.5 = d Hope this helped!
