Points C and D are marked on the segment AB. Find AD if AC = 1.2 cm, BC = 5 cm, BD = 3.8 cm.

To solve this problem, we need to find the length of the segment CD, since the length of the segment AD consists of the sum of the lengths of the segments AC and CD. The segment BD belongs to the segment BC (i.e. the segment BD is included in the segment BC), therefore, to find the segment CD, it is necessary to subtract the segment BD from the segment BC.
Decision:
1) СD = BC – BD;
2) CD = 5 – 3.8;
3) CD = 1.2;
4) AD = AC + CD;
5) AD = 1.2 + 1.2;
6) AD = 2.4.
Answer: AD = 2.4 centimeters.
Verification:
1) AC + CB = 1.2 + 5 = 6.2;
2) AD + BD = 2.4 + 3.8 = 6.2;
3) 6.2 = 6.2