(√a) 5. (-3)x-(5) 6. -5/100 7. 3/2+3/5 8. (1/2)(1/2)(-1/3) 9. 2/5+1/7 10. 12x4/47x3 11. (3b²)x(a³)/9a5b

$$(2)^2 = 4$$

The simplified answer is $\boxed{\text{4}}$.

2.5.

$$9 \times 25 = 225$$

The simplified answer is $\boxed{\text{225}}$.

2.6.

$$-5 \frac{91}{100} = -5.91$$

The decimal form is $\boxed{\text{-5.91}}$.

2.7.

$$\frac{21 + 104}{28} = \frac{125}{28}$$

The simplified answer is $\boxed{\frac{125}{28}}$.

2.8.

$$\frac{-2}{30} = -\frac{1}{15}$$

The simplified answer is $\boxed{-\frac{1}{15}}$.

2.9.

$$\frac{3 \times 7}{5 \times 2} = \frac{21}{10}$$

The simplified answer is $\boxed{\frac{21}{10}}$.

2.10.

$$3x$$

The simplified answer is $\boxed{\text{3x}}$.

2.11.

$$(3b^2)^3 = 3^3 (b^2)^3 = 27b^6$$ $$(a^3)^2 = a^{3 \times 2} = a^6$$

$$27b^6 \times a^6 = 27a^6b^6$$

The simplified answer is \boxed{\text{27a^6b^6}}.

2.12.

$$4x \times x = 4x^2$$ $$5x \times x = 5x^2$$

$$4x^2 - 5x^2 = -x^2$$

The simplified answer is \boxed{\text{-x^2}}.

2.13.

$$7x \times 3 = 21x$$

The simplified answer is $\boxed{\text{21x}}$.

2.14.

$$4x \times x^2 = 4x^{1+2} = 4x^3$$

The simplified answer is \boxed{\text{4x^3}}.

2.15.

$$(-3x^2y)(-3xy^2)(-3x^2y)(-3xy^2)$$ $$= ((-3) \times (-3) \times (-3) \times (-3)) \times (x^2 \cdot x \cdot x^2 \cdot x) \times (y \cdot y^2 \cdot y \cdot y^2)$$ $$= 81 \times x^{2+1+2+1} \times y^{1+2+1+2}$$ $$= 81x^6y^6$$

The simplified answer is \boxed{\text{81x^6y^6}}.

2.16.

$$\frac{7b(x^3 + 2ab)}{7ab} = \frac{x^3 + 2ab}{a}$$

The simplified answer is $\boxed{\frac{x^3 + 2ab}{a}}$.

2.17.

$$4 + 2x = 12$$ $$2x = 12 - 4$$ $$2x = 8$$

$$x = \frac{8}{2}$$ $$x = 4$$

The solution is $\boxed{\text{x=4}}$.

2.18.

$$2x = 3 - 2$$ $$2x = 1$$

$$x = \frac{1}{2}$$

The solution is $\boxed{x=\frac{1}{2}}$.

2.19.

$$4x - 3(x-4) = 3 - 2x$$ $$4x - 3x + 12 = 3 - 2x$$

$$x + 2x + 12 = 3$$ $$3x + 12 = 3$$

$$3x = 3 - 12$$ $$3x = -9$$

$$x = \frac{-9}{3}$$ $$x = -3$$

The solution is $\boxed{\text{x=-3}}$.

2.20.

$$\frac{15 \div 5}{100 \div 5} = \frac{3}{20}$$

The answer as a common fraction is $\boxed{\frac{3}{20}}$.

2.21.

$$(-0.5)^3 = (-0.5) \times (-0.5) \times (-0.5) = 0.25 \times (-0.5) = -0.125$$

The answer rounded to three decimal places is $\boxed{\text{-0.125}}$.

QUESTION 3

3.1. Consider the following pattern $-7; -11; -15; ...$

3.1.1.
The rule is to subtract 4 from the previous term.

3.1.2.

$$-11 - (-7) = -4$$ $$-15 - (-11) = -4$$

The common difference is $\boxed{\text{-4}}$.

3.1.3.

$$-19 + (-4) = -23$$

The next two terms are $\boxed{\text{-19; -23}}$.

3.1.4.

$$T_n = -7 - 4n + 4$$ $$T_n = -4n - 3$$

The rule is $\boxed{T_n = -4n - 3}$.

3.1.5.

$$T_{30} = -120 - 3$$ $$T_{30} = -123$$

The 30th term is $\boxed{\text{-123}}$.

3.2.

$$1.23 \times 10^{-7} = 0.000000123$$

The number in full is $\boxed{\text{0.000000123}}$.

3.3.
This question is incomplete. Please provide the full question.