If$\mathrm{k}+3, 2, 3\mathrm{k} \mathrm{and} 3$ are in proportion then the value of k is ________.

If$\mathrm{k}+3, 2, 3k \mathrm{and} 3$ are in proportion then,

We can say that  $\frac{\mathrm{k}+3}{2}=\frac{3k}{3}$

By cross multiplication:

$(\mathrm{k}+3) \times 3= 2 \times 3\mathrm{k}$

or $3\mathrm{k} + 9 = 6\mathrm{k}$

or $9 = 6\mathrm{k} - 3\mathrm{k}$ 

or $9 = 3\mathrm{k}$

or $\mathrm{k}=\frac{9}{3}$

or $\mathrm{k}=3$