The square of a binomial expands as follows:

Expanding all the binomials, we have

Sum like terms:

Simplify terms appearing on both sides:

Move all terms involving k to the left and all numbers to the right:

Divide both sides by -20:

Answer: BC = 54 <kjm=44
Step-by-step explanation:
1st 0ne-
if you look at it as 2 triangles with D being the shared side- I can determine that the angles are congruent (by SSA theorem)
so
6x=9x-27 (by corresponding parts of congruent Theorem)
-3x=-27
x=9
BC- 9(9)-27= 81-27=54
2nd one-
J bisects KJM
4x+6=3x+10
x=4
3(4)+10= 22
4(4)+6= 22
KJM= 22+22= 44