1) Sketching it
Since the line segment AD = 10x -5 and AC= 3x +1 and CD= 15
According to the Segment Addition postulate we can write:
3x+1+15=10x-5 Combining like terms
3x +16 = 10x -5 Subtract 16 from both sides
3x = 10x-5-16 Subtract 10x from both sides
3x-10x =-21
-7x = -21
7x=21 Dividing by 7 on both sides
x=3