Show steps as well ! i will mark brainiest

4

Step-by-step explanation:

Alright we know the equation AB+BC=AC is the postulate formula given for AC length.

So we do algebraic equation here which would be

(4m-15)+(5m-6)=15

Remove parenthesis

4m-15+5m-6=15

Combine like terms:

9m-21=15

Add 21 to other side

9m=15+21

9m=36

Divide 9

m=36/9

m=4

So the last multiple choice there :)

-8

Step-by-step explanation:

,,lkk