The percentage of students who like only writing is 40% - 10% = 30%.

The percentage playing only cricket is 60% - 10% = 50%, and only football is 40% - 10% = 30%. Thus, total playing only one sport is 50% + 30% = 80%.

6a + 4 = 28 => 6a = 24 => a = 4.

6x + 4 > 10 => 6x > 6 => x > 1.

7 - 2x > 3 => -2x > -4 => x < 2.

7 - 2x ≥ 1 => -2x ≥ -6 => x ≤ 3

7 - 2x ≥ 3 => -2x ≥ -4 => x ≤ 2.

7 - 3x ≤ 1 => -3x ≤ -6 => x ≥ 2.

7 - 3x ≥ 1 => -3x ≥ -6 => x ≤ 2.

Using inclusion-exclusion, the percentage of students who play either sport is 70% + 50% - 20% = 100%.

7x + 1 ≥ 15 => 7x ≥ 14 => x ≥ 2

Subtracting 4x from both sides gives 3x - 3 = 6, then adding 3 gives 3x = 9, leading to x = 3.

Dividing both sides by 7 gives x = 3.

To solve 7x ≡ 3 (mod 5), we first reduce 7 mod 5 to get 2x ≡ 3 (mod 5). The solution is x ≡ 4 (mod 5), which corresponds to 2.

Since 1/49 can be expressed as 7^(-2), we have 7^x = 7^(-2), thus x = -2.

49 = 7^2, so x = 2.

8b + 16 = 48 => 8b = 32 => b = 4.

Dividing both sides by 4 gives 2x ≡ 1 (mod 3). The solution is x = 2.

64 = 8^2, so x = 2.

If A > B and B > C, then by transitive property, A > C is true.

Since A < B and B ≤ C, it follows that A < C.

The roots of the equation x^2 - 10x + 21 = 0 are found using the quadratic formula, yielding a = 3 and b = 7.

Using the identity a^2 + b^2 = (a + b)^2 - 2ab, we get a^2 + b^2 = 10^2 - 2*21 = 100 - 42 = 58.

Using the identity a^2 + b^2 = (a + b)^2 - 2ab, we have 70 = 12^2 - 2ab. Thus, 70 = 144 - 2ab, leading to ab = 37.

Potential Energy (PE) = m * g * h = 10 kg * 9.8 m/s^2 * 20 m = 1960 J

Using v² = u² + 2gh, v = √(0 + 2 × 10 m/s² × 20 m) = √400 = 20 m/s.

Potential energy = mgh = 10 kg × 9.8 m/s² × 5 m = 490 J.

The force due to gravity is F = mg = 10 kg * 9.8 m/s² = 98 N, which rounds to 100 N.

Kinetic Energy (KE) = 1/2 * m * v^2 = 1/2 * 10 * (4^2) = 80 J

Using F = ma, acceleration a = F/m = 30 N / 10 kg = 3 m/s².