Solving 2x + 3 < 11 gives 2x < 8, thus x < 4. The maximum integer value is 3.

From the first equation, y = (18 - 2x)/3. Substituting into the second gives 4x - (18 - 2x)/3 = 10. Solving leads to y = 4.

Rearranging gives 4 > x, thus x < 4.

Rearranging gives x > 5. Thus, the correct option is x < 5.

2y - 7 = 13 => 2y = 20 => y = 10.

If 3 machines produce 150 units, then 6 machines will produce 150 * 2 = 300 units.

Rate of production = 150 units / 5 hours = 30 units/hour for 3 machines. For 6 machines, rate = 60 units/hour. In 2 hours, they produce 60 * 2 = 120 units.

3 machines produce 150 units in 5 hours, so 6 machines will produce 300 units in 5 hours. In 10 hours, they will produce 600 units.

The ratio of A to B is 3:5.

Rate of 3 pipes = 1/12. Rate of 1 pipe = 1/36. Rate of 5 pipes = 5/36. Time taken = 36/5 = 7.2 hours, which rounds to 8 hours.

Rate of 3 pipes = 1/4 tank/hour. Rate of 1 pipe = 1/12 tank/hour. Rate of 5 pipes = 5/12 tank/hour. Time = 12/5 = 2.4 hours.

Let the number be x. Then, 3/5 * x = 30, so x = 30 * 5/3 = 50.

If 3/8 is left, then 1 - 3/8 = 5/8 has been eaten.

In a 1:2 ratio, the total parts = 1 + 2 = 3. Alcohol = (1/3) * 30 = 10 liters.

In a 2:3 ratio, the total parts = 2 + 3 = 5. Alcohol = (2/5) * 30 = 12 liters.

3a + 4 = 19 => 3a = 15 => a = 5.

Solving gives 3x > 3, thus x > 1. The minimum integer is 2.

Rearranging gives 8 < 2x, thus x > 4.

From the first equation, 4y = 24 - 3x. Substituting into the second gives 5x - 2(24 - 3x)/4 = 10. Solving this leads to y = 2.

Subtract 2x from both sides: x + 5 = 10. Subtract 5 from both sides: x = 5.

Solving gives 3x < 6, thus x < 2. The largest integer is 2.

Rearranging gives -3 < x, thus x > -3.

Solving 3x - 4 ≤ 5 gives 3x ≤ 9, thus x ≤ 3.

Solving gives 3x < 9, thus x < 3.

Add 5 to both sides: 3x = 21. Then divide by 3: x = 7.

Rate = 4 bicycles / 6 hours = 2/3 bicycles/hour. For 6 bicycles, rate = 4 bicycles/hour. In 18 hours, they can repair 4 * 18 = 72 bicycles.

Alcohol = 10% of 4L = 0.4 liters.

Work done by 4 men in 10 days = 1 work unit. Work done by 1 man in 40 days. 6 men will do it in 40/6 = 20/3 = 6.67 days, which rounds to 8 days.

Work done by 4 men in 10 days = 1 work unit. Work done by 1 man in 40 days = 1/40 work unit/day. To complete in 5 days, required rate = 1/5 work unit/day. Number of men = 1/(1/40) * 5 = 8.

If 4 people take 12 days, then to complete in 6 days, we need 4 * 12 / 6 = 8 people.