Fill in the blanks:

(i) In algebra, we use ….. to represent variables (generalized numbers).

(ii) A symbol or letter which can be given various numerical values is called a …..

(iii) If Jaggu's present age is x years, then his age 7 years from now is …..

(iv) If one pen costs ₹x, then the cost of 9 pens is …..

(v) An equation is a statement that the two expressions are ……

(vi) The numerical coefficient of the monomial −5x²y³ is …..

(vii) 7 less than thrice a number y is …..

(viii) If 3x + 4 = 19, then the value of x is …..

(ix) The number of pencils bought for ₹x at the rate of ₹2 per pencil is ……… .

(x) 3p²q and −5pq² are ….. terms.

(xi) The value of the expression 3 − 5x for x = 4 is …..