Open Sentences and Simple Equations

Remember letters can also be used to stand for the unknown numbers in open sentences.

Example 1

Find x, if 6 + x = 10

Solution

6 + x – 6 = 10 – 6

X + (6 – 6) = 4

    :. X = 4

Example 2

I think of a number, multiply it by 2 and add 4, the result is 10. Find the number.

 Solution

  Let the number be y

                    2y + 4 = 10

                     2y + 4 – 4 = 10 – 4

                               2y = 6

                                :. Y = 6/2 = 3

Home work: Find the value of the letters in the question below

    1)  x + 2 = 5    (2)  33 + a = 45

3) When 3 is added to a number the result is 15. Find the number