Solution:

3x + 4 = 28

3x = 28 - 4

3x = 24

x = 8

Therefore, the value of x = 8

Example 2: Five less than a number equals to two. What is the number?

Solution:

Using the concepts of Algebra, we will assume the number to be a variable. Let the number be x. As per the question, we can write x - 5 = 2. On solving this, we get x = 7. Therefore, the required number is 7.

Addition: x + y

Subtraction: x – y

Multiplication: xy

Division: x/y or x ÷ y

where x and y are the variables.

The order of these operations will follow the BODMAS rule, which means the terms inside the brackets are considered first. Then, roots and exponents are operated on second priority. Solve all the division and multiplication operations and later addition and subtraction.

a2 – b2 = (a – b)(a + b)

(a+b)2 = a2 + 2ab + b2

a2 + b2 = (a – b)2 + 2ab

(a – b)2 = a2 – 2ab + b2

(a + b + c)2 = a2 + b2 + c2 + 2ab + 2ac + 2bc

(a – b – c)2 = a2 + b2 + c2 – 2ab – 2ac + 2bc

(a + b)3 = a3 + 3a2b + 3ab2 + b3

(a – b)3 = a3 – 3a2b + 3ab2 – b3

These fomulas are used in higher secondary classes. Students can find algebra formulas for class 8, along with class 9, class 10, class 11 and class 12 here.

Solution: y = 30 – 15

y = 15

•Find x, when, 9x = 63

 Solution:x = 63/9

x = 7

•If x/7 = 21, then find x.

Solution: Given x/7 = 21

or x = 21 x 7

x = 147