Use of scalar variables

$a=4$

$b=5$

$c=12$

Please find the following:

$D=a-b$

$x=a**cos\frac{d}{b+c}$

$y=x^{{?}^{{?}^{?}}}3$;

Exercise $4$

Use the following code to generate a graph

$T=-2$:$0\mathrm{.}1$:$2$;

Subplot$(2,2,1)$;

Plot$($t$,$t$)$;

Subplot$(2,2,2)$;

Plot$($t$,$t$.^2)$;

Subplot$(2,2,3)$;

plot$($t$,$t$.^3)$;

subplot$(2,2,4)$;

Plot$($t$,$t$.^4)$;