Expression palette: Definite-integral template
As per the discussion above, enter the equation that governs the work done in stretching the spring from 5 to 10 inches.  

Press the Enter key.

$\frac{1}{2}k\left({\left(10-L\right)}^2-{\left(5-L\right)}^2\right)\=25$

Expression palette: Definite-integral template
As per the discussion above, enter the equation that governs the work done in stretching the spring from 10 to 14 inches.  

Press the Enter key.

$\frac{1}{2}k\left({\left(14-L\right)}^2-{\left(10-L\right)}^2\right)\=40$

Using equation labels, construct a sequence of these two equations.
Press the Enter key.

Context Panel: Solve≻Solve