Lake inflow-outflow problem
Everything you did looks reasonable.  There is one error in the 'net inflow into lake' line where you take the area of the lake to be $100\cdot10^3\ \text{m}^2$ instead of $100\cdot10^6\ \text{m}^2$, but that might just be a typo.  

In general, this type of problem is much easier to work (especially when you think you've made an error) by keeping everything symbolic.  For your problem I would define the variables


$i$: inflow into the river in $\frac{\text{m}^3}{\text{s}}$
$o$: outflow from the river in $\frac{\text{m}^3}{\text{s}}$
$r$: inflow from rain in $\text{m}$
$e$: evaporation in $\text{m}^3$
$\Delta h$: change in height of the lake in $\text{m}$
$A$: area of the lake in $\text{m}^2$
$\Delta t$: time period in $\text{s}$


The equilibrium equation is then 

$$\text{sum of inflows}-\text{sum of outflows}=\text{change in storage}$$

which is written in terms of the defined variables as

$$i\ \Delta t+r\ A-o\ \Delta t-e=\Delta h\ A.$$

You can check that this equation at least makes sense in terms of units by observing that all of the terms have units of volume, i.e. $\text{m}^3$.  Finally, you can rearrange the equation to solve for the variable of interest;

$$e=(i-o)\Delta t+(r-\Delta h)A.$$

At this point you can plug in the numbers.