What is the net force on the block if it is moved 15 to the right of its equilibrium position? Hint: There is zero net force on the point where the two springs meet. This implies a relationship between the amounts the two springs stretch

Your question isn't clear. If you mean the If the block is attached to a spring and the spring is attached to a rigid wall, then the net force on the block when moved from its equilibrium position would be the spring constant times the displacement in the direction opposite to the displacement of block.