State whether the following statements are true (T) or false (F):

(i) If x is variable then 5x is also variable.

(ii) If y is variable then y − 5 is also variable.

(iii) The number of angles in a triangle is a variable.

(iv) The value of an algebraic expression changes with the change in the value of the variable.

(v) If the length of a rectangle is twice its breadth, then its area is a constant.

(vi) An equation is satisfied only for a definite value of the variable.

(vii) If x toffees are distributed equally among 5 children, then each child gets 5x toffees.

(viii) t minutes are equal to 60t seconds.

(ix) If x is a negative integer, then −x is a positive integer.

(x) x = 5 is a solution of the equation 3x + 2 = 13.

(xi) 2y - 7 > 13 is an equation.

(xii) 'One third of a number x added to itself gives 8' can be expressed as $\dfrac{x}{3} + 8 = x$.

(xiii) The difference between the ages of two sisters Lata and Asha is a variable.

(i) True. The value of 5x depends on the value of x, so 5x is a variable.

(ii) True. The value of y − 5 depends on the value of y, so y − 5 is a variable.

(iii) False. The number of angles in any triangle is always 3, which is a constant.

(iv) True. The value of an expression depends on the value of the variable.

(v) False. If breadth is b, then length = 2b and area = 2b², which depends on b. So the area is a variable.

(vi) True. A linear equation in one variable has exactly one solution.

(vii) False. Each child gets $\dfrac{x}{5}$ toffees, not 5x.

(viii) True. Since 1 minute = 60 seconds, t minutes = 60t seconds.

(ix) True. The additive inverse of a negative integer is positive.

(x) False. At x = 5, 3x + 2 = 3(5) + 2 = 17, which is not equal to 13.

(xi) False. 2y - 7 > 13, it is an inequality, not an equation.

(xii) False. The correct expression is $\dfrac{x}{3} + x = 8$ (or $x + \dfrac{x}{3} = 8$).

(xiii) False. The difference between the ages of two persons remains the same throughout their lives, so it is a constant.