The minimum spanning tree is the one that connect every vertex just one time with the smallest length possible
In the picture, if we remove the segments CG, FG, CD, CF, HD and AK, we get the minimum spanning tree, with length KC + AB + BC + BE + ED + DF + FH + HG = 10 + 2 + 3 + 3 + 2 + 2 + 2 + 1 = 25 units