What is the name of the polygon with sum of interior angles 1080 degrees? Find the number of sides of a regular polygon if the sum of interior angles is 1080 degrees.

$$n-2 = \frac{1080}{180}$$ $$n-2 = 6$$

$$n = 6 + 2$$ $$n = 8$$

A polygon with 8 sides is called an octagon.
The name of the polygon is $\boxed{\text{Octagon}}$.

$$\text{Fraction (food + rent)} = \frac{1}{3} + \frac{1}{4}$$ $$\text{Fraction (food + rent)} = \frac{4}{12} + \frac{3}{12} = \frac{7}{12}$$

He spent $\frac{1}{2}$ of the remainder on school fees.

$$\text{Fraction (school fees)} = \frac{1}{2} \times \frac{5}{12} = \frac{5}{24}$$

The fraction saved is the remainder minus the fraction spent on school fees.

$$\text{Fraction saved} = \frac{5}{12} - \frac{5}{24}$$ $$\text{Fraction saved} = \frac{10}{24} - \frac{5}{24} = \frac{5}{24}$$

The fraction of the salary he saved is $\boxed{\frac{5}{24}}$.

Let $S$ be the total salary.

$$\frac{5}{24} \times S = 4800$$ $$S = 4800 \times \frac{24}{5}$$ $$S = 960 \times 24$$ $$S = 23040$$

Ethan's total salary is sh 23,040.

$$\text{Amount (rent)} = \frac{1}{4} \times S$$ $$\text{Amount (rent)} = \frac{1}{4} \times 23040$$ $$\text{Amount (rent)} = 5760 \text{ sh}$$

$$\text{Amount (food)} = \frac{1}{3} \times S$$ $$\text{Amount (food)} = \frac{1}{3} \times 23040$$ $$\text{Amount (food)} = 7680 \text{ sh}$$

$$\text{Difference} = \text{Amount (rent)} - \text{Amount (food)}$$ $$\text{Difference} = 5760 - 7680$$ $$\text{Difference} = -1920 \text{ sh}$$

The negative sign indicates that sh 1920 less was spent on rent than on food.
The amount is $\boxed{-1920 \text{ sh}}$.