Simplify the following mathematical expressions: k) 55 / 11 [120 / 2 \4 + (10 + 5 - 7)\], l) (7 x 6) / 2 [\45 / 3(7 x 2 - 1)\], and a) 4 times the sum of 7 and 2.

here are the solutions for the remaining questions.

4. Let's simplify.

k) $55 \div 11 [120 \div 2 \{4 + (10 + 5 - 7)\}]$

Step 1: Perform operations inside the innermost parentheses.

$$55 \div 11 [120 \div 2 \{4 + (15 - 7)\}]$$ $$55 \div 11 [120 \div 2 \{4 + 8\}]$$

Step 2: Perform the addition inside the curly braces.

$$55 \div 11 [120 \div 2 \{12\}]$$

Step 3: Perform division and multiplication inside the square brackets from left to right.

$$55 \div 11 [60 \times 12]$$ $$55 \div 11 [720]$$

Step 4: Perform the division.

$$5 \times 720$$

Step 5: Perform the multiplication.

$$3600$$ $$\boxed{3600}$$

l) $(7 \times 6) \div 2 [\{45 \div 3(7 \times 2 - 1)\}]$

Step 1: Perform the operation inside the innermost parentheses.

$$(7 \times 6) \div 2 [\{45 \div 3(14 - 1)\}]$$ $$(7 \times 6) \div 2 [\{45 \div 3(13)\}]$$

Step 2: Perform the division inside the curly braces.

$$(7 \times 6) \div 2 [\{15 \times 13\}]$$

Step 3: Perform the multiplication inside the curly braces.

$$(7 \times 6) \div 2 [195]$$

Step 4: Perform the multiplication outside the brackets.

$$42 \div 2 [195]$$

Step 5: Perform the division.

$$21 \times 195$$

Step 6: Perform the multiplication.

$$4095$$ $$\boxed{4095}$$

5. Let's make the mathematical expressions and simplify.