Identify the variables, terms and number of terms in each of the following expressions:
(i)12 −x
(ii) 7 + 2y
(iii) 29 + 3x + 5y
(iv) 3x – 5 + 7z

Find the numerical co-efficient of the following terms. Also, find the co efficient of x and y in each of the term: 3x, - 5xy, - yz, 7xyz, y, 16yx.

If x = 3, y = 2 find the value of
(i) 4x + 7y
(ii) 3x + 2y − 5
(iii) x − y

Find the value of
(i) 3m + 2n
(ii) 2m − n
(iii) mn − 1, given that m = 2, n = − 1.

Find two consecutive natural numbers whose sum is 75.