How old is Sky now?

• Let Sky's age now be $x$ .
• Marvin was at Sky's present age $33-x)$ years ago.
• Sky's age then was $x-(33-x) = 2x-33$ .
• And three times Sky's age then is Marvin's age now and in equation

$\begin{aligned} 3(2x-33) & = 33 \\ 2x-33 & = 11 \\ 2x & = 44 \\ \implies x & = \boxed{22} \end{aligned}$

Let Sky be $x$ years old now. Then the given informations yield

$33=3(2x-33)\implies x=\dfrac{33\times 4}{6}=\boxed {22}$ . So Sky is $\boxed {22}$ years old now.

$M=33$

$M=3(S-x)$

$33=3(S-x)$

$11=S-x$

$x=S-11$ $[\text{equation 1}]$

$M-x=S$

$33-x=S$ $[\text{equation 2}]$

Now, substitute the value of $x$ in $[\text{equation 1}]$ into $[\text{equation 2}]$

$33-x=S$

$33-(S-11)=S$

$33-S+11=S$

$2S=44$

$S=\boxed{22}$