Question

Without solving determine whether the solution of 1/3x = 21 is greater than or less than 21. Explain

Answer 1

Without solving, the solution is greater than 21.  The can be proven because a fraction of x is equal to 21, therefore x cannot be less than 21.  

Answer 2

Solving the linear equation

 $\rightarrow\frac{x}{3}=21\\\\\text{Multiplying by 3 on both sides}\\\\\rightarrow\frac{x}{3} \times 3=21\times 3\\\\x=63$

→63>21,

that is, solution of the linear equation is greater than 21.