Question

if energy can neither be created nor be destroyed then how does it exist ?

Answer 1

Energy is neither created nor destroyed but it can be transformed from one form to another
Example: solar energy from sun is converted to electrical energy

Answer 2

i can't explain it fully but i will try at my level..

see..we can't create or destroy energy now..
all the energy which was created at the time of creation of universe or say at the time of big bang that much energy is present in this universe which keeps changing its form and thus now we can't create or destroy energy.