The first law of thermodynamics states that when a process converts energy from one form to another, some energy converted into heat, an unusable form of energy energy can neither be created nor destroyed, but it can change from one form to another energy flows through ecosystems without being recycled most energy in ecosystems comes from the sun

The answer is: energy cannot be created or destroyed under normal conditions

The first law of thermodynamics was introduced by  Rudolf Clausius and  William Rankine in the year of 1950s. It stated that The energy cannot be destroyed or created, but it can be changed/altered. 'Normal' conditions in this context refers to the condition where the energy is not being intervened by external factors in any way.

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.