There are two things that you should remember while dealing with the "Lever Mechanical Advantage" problems:
1) The Effort Arm;
2) The Resistance Arm.
Some books label the Effort Arm as in-lever arm and the Resistance Arm as out-lever arm. (Physics Jargon that you need to remember in order to solve problems)
The Effort Arm is that "part" of the lever where the force can be applied. The Resistance Arm is where some mass is placed. In the diagram, as you can see, the mass is placed on one arm of the lever. Therefore, it is the Resistance Arm.
Now the formula for the "Mechanical Advantage(MA)" is:
Where
is the length of the Effort Arm(the subscript "e" stands for Effort), and 
stands for the length of the Resistance Arm(here "r" stands for Resistance).
Plug in the values:
= 15m.
= 7m.
Therefore, / = 15/7 = 2.143 = MA
The correct answer is option C(2.14).
-i
1) The Effort Arm;
2) The Resistance Arm.
Some books label the Effort Arm as in-lever arm and the Resistance Arm as out-lever arm. (Physics Jargon that you need to remember in order to solve problems)
The Effort Arm is that "part" of the lever where the force can be applied. The Resistance Arm is where some mass is placed. In the diagram, as you can see, the mass is placed on one arm of the lever. Therefore, it is the Resistance Arm.
Now the formula for the "Mechanical Advantage(MA)" is:
Where
Plug in the values:
Therefore,
The correct answer is option C(2.14).
-i