The equation is a scientific law, Newton's Law of Gravity,

This is a pretty bad question. Newton's Law of Gravity is a mathematical model of gravitation, originally a theory, verified by observation, and now superseded by the General Theory of Relativity.
C is probably the best answer to this poor question.
X= first number
x+1= second number
2x+1=275
2x=274
x+274
x=137 first number
137+1=138 second number