Convert the mixed percentage to a decimal.

$$7\frac{1}{2}\% = 7.5\%$$

To convert a percentage to a decimal, divide by 100.

$$7.5\% = \frac{7.5}{100} = 0.075$$

$$0.075 \times 236$$ $$0.075 \times 236 = 17.7$$

The currency unit is K.
The answer is K17.70.

$$\boxed{\text{K17.70}}$$

The "whole" is K30 816 and the "part" is K2 311.2.

$$\text{Percentage} = \frac{2311.2}{30816} \times 100\%$$

$$\frac{2311.2}{30816} = 0.075$$ $$0.075 \times 100\% = 7.5\%$$ $$\boxed{7.5\%}$$