Segment LR with point P between L and R

If LP = 15 and PR = 9, find LR. Explain.

LR = 24 because 15 + 9 = 24 according to the addition property of equality.
LR = 6 because LR + LP = PR according to the Segment Addition Postulate, and 6 + 9 = 15 using substitution.
LR = 24 because LP + PR = LR according to the Segment Addition Postulate, and 15 + 9 = 24 using substitution.
LR = 6 because 15 − 9 = 6 according to the subtraction property of equality.