Solve the following math problems: 1. 1.03 6 = ? 2. Convert 72 (base 10) to binary. 3. Simplify 0.25 100 + 10 * 2.5 = ? 4. 2/3 - 1/4 = ? 5. Find the next number in the sequence: 9, 3, 1, 1/3, ...

$$0.25 \times 100 = 25$$ $$10 \times 2.5 = 25$$

$$25 + 25 = 50$$

The answer is $\boxed{50}$.

4. Subtract $\frac{2}{3} - \frac{1}{4}$

$$\frac{2}{3} = \frac{2 \times 4}{3 \times 4} = \frac{8}{12}$$ $$\frac{1}{4} = \frac{1 \times 3}{4 \times 3} = \frac{3}{12}$$

$$\frac{8}{12} - \frac{3}{12} = \frac{8 - 3}{12} = \frac{5}{12}$$

The answer is $\boxed{\frac{5}{12}}$.

5. Find the next number in the sequence below: 9, 3, 1, \frac{1}{3}, \text{___}
Observe the pattern: each term is obtained by dividing the previous term by 3.
$9 \div 3 = 3$
$3 \div 3 = 1$
$1 \div 3 = \frac{1}{3}$
Following this pattern, the next term is:

$$\frac{1}{3} \div 3 = \frac{1}{3} \times \frac{1}{3} = \frac{1}{9}$$

The next number in the sequence is $\boxed{\frac{1}{9}}$.

6. Write 20,015 in words
The number 20,015 written in words is Twenty thousand fifteen.

7. A farmer has roll of string of long [length missing], he cuts it into equal pieces, each 50 metres long. How many pieces does he get altogether?
The total length of the roll of string is missing from the question.
If the total length of the string roll were known (let's say $L$ metres), the number of pieces would be calculated by dividing the total length by the length of each piece:

$$\text{Number of pieces} = \frac{\text{Total length of string}}{\text{Length of each piece}}$$ $$\text{Number of pieces} = \frac{L \text{ metres}}{50 \text{ metres}}$$

Without the total length of the string, the exact number of pieces cannot be determined.