In the first equation, is the gravitational potential energy, m is the mass of the object, is the magnitude of the acceleration due to gravity, and h is the height of the object above some arbitrary point.
In the second equation, is the spring potential energy, k is the spring constant, and Δx is the displacement from the unstretched spring length.
In the third equation, K is the kinetic energy, m is the mass of the object, and v is the speed.
In the fourth equation, is the work done by friction, which is converted into heat, is the force of friction, and Δx is the total distance the object moved while being acted on by the frictional force.
...which means now we know almost everything we need to know to apply conservation of energy.