18 would be the 7th so... hope it helps
Answer:
see below
Step-by-step explanation:
Since AB + BC = AC, x + 3x = 20 → 4x = 20 → x = 5.
AB = x = 5 and BC = 3x = 3 * 5 = 15.
Answer: I got C) 10.8
Step-by-step explanation:
5+23= 28 .........................