Solve the following problems: 6. 1/3 of 15 + [3-2+1] 7. 3 1/2 + 3/4 * 2/5 8. Write 57 in tally system.

Here are the solutions to the problems:

6. $\frac{1}{3}$ of $15 + [3-2+1]$

Step 1: Evaluate the expression inside the brackets.

$$3 - 2 + 1 = 1 + 1 = 2$$

Step 2: Calculate "$\frac{1}{3}$ of 15". "Of" means multiplication.

$$\frac{1}{3} \times 15 = \frac{15}{3} = 5$$

Step 3: Add the results from Step 1 and Step 2.

$$5 + 2 = 7$$

The final answer is $\boxed{7}$.

7. $3\frac{1}{2} + \frac{3}{4} \times \frac{2}{5}$

Step 1: Convert the mixed number to an improper fraction.

$$3\frac{1}{2} = \frac{(3 \times 2) + 1}{2} = \frac{7}{2}$$

Step 2: Perform the multiplication first according to the order of operations.

$$\frac{3}{4} \times \frac{2}{5} = \frac{3 \times 2}{4 \times 5} = \frac{6}{20}$$

Step 3: Simplify the multiplied fraction.

$$\frac{6}{20} = \frac{3}{10}$$

Step 4: Add the fractions $\frac{7}{2}$ and $\frac{3}{10}$. Find a common denominator, which is 10.

$$\frac{7}{2} = \frac{7 \times 5}{2 \times 5} = \frac{35}{10}$$

Step 5: Add the fractions.

$$\frac{35}{10} + \frac{3}{10} = \frac{35+3}{10} = \frac{38}{10}$$

Step 6: Simplify the final fraction.

$$\frac{38}{10} = \frac{19}{5}$$

The final answer is $\boxed*{\frac{19}{5} \text{ or } 3\frac{4}{5}*}$.

8. Write the following in tally system:

i) 57

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