First law of thermodynamics is mathematically stated as

First law of thermodynamics sates that energy can’t be destroyed instead it converts from one form to another form only. The two forms of energy in transits are heat and work with which the system contacts the surroundings there by changing its internal energy:
If we express this in mathematical form:
\[\delta Q=dU+\delta W\]
Where,
\[\delta Q=\text{ heat given to the system}\]
\[\delta W=\text{work done by the system}\]