Given,
National Income $\left(\mathit{Y}\right)=2000$
Autonomous consumption expenditure $=200$
Investment expenditure $=100$
As we know in equilibrium,
$\mathit{Y}=\mathit{C}+\mathit{I}$
Since, $\mathit{C}=\mathit{C}+\mathit{c}\mathit{Y}$
We get $\mathit{Y}=\mathrm{C}+\mathit{c}\mathit{Y}+\mathrm{I}$
$2000=200+\mathit{c}\left(2000\right)+100$
$1700=2000\mathit{c}$
$\Rightarrow \mathit{c}=0.85$
Therefore, marginal propensity to consume is 0.85 .