 In this video we're asked to solve for X given the information that M is the midpoint of ND. Keep in mind that in the previous problems we've used the midpoint formula any time we see this word midpoint but this problem we're going to approach a little bit differently. The midpoint formula is only used when we have XY coordinates or we're given a graph to work with. This problem, these aren't XY coordinates. These are given values for expressions on this line segment. So we're going to use the information that M is the midpoint in a different way. If this segment ND has M as the midpoint that just means that segment NM and segment MD are equal in measure and we can say they're actually congruent. You'll hear that term a lot. We could say NM is congruent to MD. We're going to use that information to set up an equation and solve for X. If we know that those two segments are equal then we can set up an equation 2X plus 5 equals 23 and you'll see that whenever we're asked to solve for X usually we're going to set up an equation and solve with algebra. So now that we have our equation this is a simple one step equation where we want to get X by itself and we get 2X equals 18 and the last step divide both sides by 2 and we get X equals 9. We were asked to solve for X, X equals 9. So as you're going through these problems keep in mind when they're talking about the midpoint you're not always going to use the midpoint formula. If you're given information that aren't coordinate points like this you'll want to set up an equation to solve the problem.