This is an isosceles triangle, therefore we have two sides with the same length.
This sides are JM and MK; therefore:
JM=MK
JM=9x-18
MK=3x
Therefore:
9x-18=3x
9x-3x=18
6x=18
x=18/6
x=3
Part A:
Answer: x=3
Part B:
JM=9x-18=9(3)-18=27-18=9
Answer: JM=9
