Determine the percentage rate of taxation paid by ai. Mr Ade in column X and Y ii. Mr Uche in column X and Y iii. Alhaji Gbadamosi in column Y

Mr Ade's percentage tax rates are: Column X: \boxed{\text{10%}}, Column Y: \boxed{\text{8%}}

Mr Uche's percentage tax rates are: Column X: \boxed{\text{10%}}, Column Y: \boxed{\text{5%}}

Alhaji Gbadamosi's percentage tax rate in column Y is: \boxed{\text{8.67%}}

• Mr Ade: 10%
• Alhaji Gbadamosi: $\frac{1500}{15000} \times 100\% = 10\%$
• Mr Uche: 10% In column X, the tax rate remains constant regardless of the income base. This is a proportional tax system.

• Mr Ade: 8%
• Alhaji Gbadamosi: 8.67%
• Mr Uche: 5% In column Y, as income increases (10,000 to 15,000 to 30,000), the percentage tax rate generally decreases (8% to 8.67% to 5%). This is a regressive tax system.

The system of taxation employed is: Column X: $\boxed{\text{Proportional Tax}}$, Column Y: $\boxed{\text{Regressive Tax}}$

• Mr Ade: 8%
• Alhaji Gbadamosi: 8.67%
• Mr Uche: 5% The least percentage tax rate indicates the least burden.

The income earner with the least burden under column Y is: $\boxed{\text{Mr Uche}}$