Simplify 7-5, construct a right angle using only a ruler, pencil, and compasses, and convert 500 Euros to Uganda shillings given 1 Euro = 4,400 Ug sh.

$$7 - 5 = 2$$

The simplified value is $\boxed{2}$.

11. Using a ruler, a sharp pencil and a pair of compasses only, construct a right angle in the space below.
To construct a right angle (90 degrees):

1. Draw a straight line and mark a point P on it.
2. Place the compass needle on P and draw arcs of the same radius to intersect the line on both sides of P. Label these intersection points A and B.
3. With the compass needle on A, open the compass to a radius greater than AP, and draw an arc above the line.
4. With the compass needle on B and using the same radius as in step 3, draw another arc to intersect the previous arc. Label this intersection point C.
5. Draw a straight line from P to C. The angle formed at P (e.g., $\angle APC$) will be a right angle ($90^\circ$).

12. Given that 1 Euro = Ug sh. 4,400 at a forex bureau. Convert 500 Euro to Uganda shillings.

$$500 \text{ Euro} \times \frac{4,400 \text{ Ug sh.}}{1 \text{ Euro}}$$ $$500 \times 4,400 = 2,200,000$$

500 Euro is equal to $\boxed{2,200,000 \text{ Ug sh.}}$.