Given the following answer.
You want to find the value of x, the value of x is the entire base length of the given triangle.
We know that a small part of the given value of x is 36
We also know that the largest part of the second triangle is 60
We can go ahead and cut off the options C and D speaking how it wouldn't make sense for the entire base length of the two triangles combined to be 48 and 12.
36 + 64 = 100
The second triangles base length is 64, combined with the base length of the first triangle its 100.
Your best answer is option B.