What is the internal energy change when $X \ J$ of work is done on the system and $Y \ J$ of heat is transferred to the surrounding?

The first law of thermodynamics is only:

Given below are two statements.
Statement-$I$ : Adiabatic work done is positive when work is done on the system and internal energy of the system increases.
Statement-$II$ : No work is done during free expansion of an ideal gas.
In the light of the above statements,choose the correct answer from the options given below.

“The mass and energy both are conserved in an isolated system”,is the statement of

Give the mathematical expression for the first law of thermodynamics.

$A$ gas expands isothermally against a constant external pressure of $1 \ bar$ from $10 \ dm^3$ to $20 \ dm^3$ by absorbing $800 \ J$ of heat from the surroundings. Calculate the value of $\Delta U$. (in $J$)