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In mathematics, a variable (usually an English alphabet) standing for an unknown value in any equation or Algebraic Expression. In general we used x, y, z or t (time) , d (distance) and r for radius.

Algebraic expressions include at least one variable and at least one operation (addition, subtraction, multiplication, division).

For example, 7(6y + 9z) is an algebraic expression.

Rules of Multiplication of Integers

RULE 1: The product of a positive integer and a negative integer is negative.

RULE 2: The product of two positive integers is positive.

RULE 3: The product of two negative integers is positive.

Rule:The product of two positive integers is positive.

To evaluate the expression\[p\,q\], substitute the value of p as 12; q = 15 and multiply 12 with 15.

When p = 12; q = 15 and the expression p qis$p q  = 12  ·  15  =  180$

Thus, the value of the expression is 180.