To find out what fraction of their pencils each person used up, we first calculate how many pencils each had left after using some.

Initially:

• Ravish had 20 pencils
• Shikha had 50 pencils
• Priya had 80 pencils

After 4 months:

• Ravish used up 10 pencils, so he has 20 - 10 = 10 pencils left
• Shikha used up 25 pencils, so she has 50 - 25 = 25 pencils left
• Priya used up 40 pencils, so she has 80 - 40 = 40 pencils left

Now, let's find the fraction of pencils each person used up:

1. Ravish: Fraction used = (Number of pencils used) / (Initial number of pencils) Fraction used = 10 / 20 = 1/2

2. Shikha: Fraction used = (Number of pencils used) / (Initial number of pencils) Fraction used = 25 / 50 = 1/2

3. Priya: Fraction used = (Number of pencils used) / (Initial number of pencils) Fraction used = 40 / 80 = 1/2

Each of them used up 1/2 of their pencils.

So, yes, each of them used up an equal fraction of their pencils. They all used up 1/2 of their pencils.

The sum of any two even numbers is always an even number.

Let's denote two even numbers as 2n2n and 2m2m, where nn and mm are integers.

The sum of these two even numbers is: 2n+2m=2(n+m)2n+2m=2(n+m)

Since nn and mm are integers, n+mn+m is also an integer. Therefore, the sum 2(n+m)2(n+m) is an even number because it is divisible by 22. Thus, the sum of any two even numbers is an even number.

To find the highest common factor (HCF) of two numbers, we find the largest number that divides both of them without leaving a remainder.

For the numbers 5 and 7, the only common factor they share is 1, since both 5 and 7 are prime numbers. Since there are no other common factors besides 1, the HCF of 5 and 7 is 1.

To find the factors of a number, you need to identify all the numbers that divide the given number evenly, including 1 and the number itself.

Let's find the factors for each:

(a) Factors of 12: 1, 2, 3, 4, 6, 12

(b) Factors of 18: 1, 2, 3, 6, 9, 18

These are all the possible factors of 12 and 18.

The only even prime number is 2. It's the only even number that is prime because by definition, an even number is divisible by 2 and no other even number (except for -2) can be prime because they are all divisible by 2 and thus not satisfying the definition of a prime number. So, the number which is even as well as prime is 2.