How much
potential energy will a linear spring have if it has a constant of
530 N/m and a displacement stretch of 0.24 m?
spring constant: k = 530 N/m
displacement: x = 0.24 m
Starting formula 

Plug in numbers with units 

Multiply: (1/2)(530)(0.24^2) = 15.264 

Final result with significant figures and unit 