As given m is a midpoint of ab. So am is half of ab.
So we can write

As given am = 3x+3 , ab = 8x - 6.
So





So x = 6.
So length of am = 3x+3 = 3*6 + 3 = 21
1.) -4x-32 2.) -6x-3 3.) -3n-28 4.) -2x-7 5.) ??? 6.) 4b-2 (I couldn't figure out #5 sorry)
1st digit: 9 possibilities (can’t have 0)
2nd digit: 10 possibilities
3rd digit:10
4th digit:10
5th digit:10
6th digit: 4 possibilities (it can only be even)
9•10•10•10•10•4 =360,000 possibilities