Answer:
AM = 38
Explanation:
Since A is the midpoint of JM, then
JA = AM = 6x - 4 , and
JA + AM = JM ← substitute values
6x - 4 + 6x - 4 = 9x + 13, that is
12x - 8 = 9x + 13 ( subtract 9x from both sides )
3x - 8 = 13 ( add 8 to both sides )
3x = 21 ( divide both sides by 3 )
x = 7
Hence
AM = 6x - 4 = (6 × 7) - 4 = 42 - 4 = 38