Can someone tell me if I did this right.

The question is: If two segments have measures equal to a third segment, the the two segments have equal measures.

My diagram had a line with a midpoint labled segment 1 and segment 2. Then I drew another segment without a midpoint equal in length to segment 1 and 2.

Given: 1+2=3

Prove: ???

Thanks in advance for the help guys. This site is very helpful and so are the people on it, I'm glad I found it. It should be very helpful in improving my grades.