Subtraction of Literals and their combination with the numbers follow the rules of subtraction of numbers.
If we are asked to subtract 5 from 7, then we write 7 – 5.
Exactly in the same way, when we are asked to subtract a number say 3 from a literal h, we write h – 3 and is read as ‘h minus 3’.
Note that h – 3 can also be read as ‘3 less than a literal number h’.
Similarly, if b is subtracted from a, we write a – b. We can also read a – b as ‘b less than a’.
If a subtracted from b, then we write b – a.
(a – b) – c means that b is subtracted from a and then c is to be subtracted from the result.
We can also say that c is subtracted from the difference of b from a.
It should be noted here that commutativity and associativity of subtraction are not true for literals as they are not true for numbers.
Examples of Subtraction of Literals:
Write each of the following phrases using number, literals and the basic operation of subtraction:
(i) 5 less than literal x
Answer: x – 5
(ii) 100 less than literal p
Answer: p – 100
(iii) Decrease x by 7
Answer: x – 7
(iv) Decrease m by n
Answer: m – n
(v) Subtract 4 from x
Answer: x – 4
(v) Subtract z from 50
Answer: 50 – z
(vi) x less than a sum of y and 7
Answer: (y + 7) – x
(vii) 10 less than a sum of x and y
Answer: (x + y) – 10
(viii) Decrease the sum of x and y by z
Answer: (x + y) – z
(ix) Decrease the sum of m and 10 by p
Answer: (m + 10) – p
(x) 5 is diminished by z
Answer: 5 - z
(xi) a less than 4
Answer: 4 - a
(xii) 4 less than x
Answer: x - 4
(xiii) Number m less than a number 10
Answer: 10 - m
(xiv) Number 7 less than a number s
Answer: s - 7
(xv) 25 taken away from y
Answer: y - 25
(xvi) x taken away from y
Answer: y - x