Final answer:
The correct answer is option B. The value of x is 7 and BM is 20.
Step-by-step explanation:
The correct answer is option B. To find the value of x, we can use the fact that M is the midpoint of AB. Since AM is equal to 3x - 1 and AB is equal to 40, we can set up the equation:
AM + MB = AB
Substituting the given values, we have:
3x - 1 + BM = 40
Next, we solve for x:
3x - 1 = 40 - BM
3x = 41 - BM
x = (41 - BM) / 3
Since M is the midpoint of AB, BM is equal to AM, which is 3x - 1. So, we can substitute BM = 3x - 1 in the equation:
x = (41 - (3x - 1)) / 3
Simplifying the equation, we get:
3x = 42 - 3x
6x = 42
x = 7
To find BM, we substitute the value of x back into the equation for BM:
BM = 3x - 1
BM = 3(7) - 1
BM = 21 - 1
BM = 20