to split some value at a certain ratio we simply divide the value by the sum of the ratios and distribute accordingly, so in this case we'll be splitting 33 by (4 + 7), let's do so,
[tex]\bf 33\qquad \stackrel{ratio}{4:7}\qquad \qquad \cfrac{4\cdot \frac{33}{4+7}}{7\cdot \frac{33}{4+7}}\implies \cfrac{4\cdot \frac{33}{11}}{7\cdot \frac{33}{11}}\implies \cfrac{4\cdot 3}{7\cdot 3}\implies \cfrac{12}{21}\qquad 12:21[/tex]
