Let the number be 100. After a 20% increase, it becomes 120. After a 20% decrease, it becomes 120 - 24 = 96. The net change is (96 - 100)/100 * 100% = -4%.

Let the number be x. Then, 5x = 45. Therefore, x = 45/5 = 9.

If a number leaves a remainder of 4 when divided by 6, it can be expressed as 6k + 4. When divided by 3, 6k is divisible by 3 and 4 gives a remainder of 1.

Let the number be x. Then, 3x - 5 = 16. Therefore, 3x = 21, and x = 21/3 = 7.

Let the original number be 10a + b. The reversed number is 10b + a. The equation is 10b + a = 10a + b - 27. Solving gives a = 7 and b = 2, so the original number is 72.

The LCM of 12 and 15 is 60, as 60 is the smallest number that both 12 and 15 divide evenly into.

The first 4 even numbers are 2, 4, 6, and 8. Their product is 2 * 4 * 6 * 8 = 384.

The sum of 3 and 4 is 7. The square of 7 is 7^2 = 49.

The first 10 prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29. Their sum is 2 + 3 + 5 + 7 + 11 + 13 + 17 + 19 + 23 + 29 = 129.

2^3 = 8 and 3^2 = 9. Therefore, 2^3 + 3^2 = 8 + 9 = 17.