Question

Check and find the error in the following solutions.

$1.$ Find the value of $x:$ $3x+x+5x=72$

$3x+x+5x=72$
$\Rightarrow 8x=72$
$\Rightarrow x=\frac{72}{8}=9$

$2.$ Find the product$:3(x-4)$

$3(x-4)=3x-4$

Answer 1

In question- 1:

$3x+x+5x\ne 8x$

$3x+x+5x=72$
$\Rightarrow 9x=72$
$\Rightarrow x=\frac{72}{9}=8$
Thus, an error was made while adding the coefficients of $x$ in the LHS.
So, the correct value for $x$ in this equation is 8 instead of 9.

In question- 2:

$3(x-4)\ne 3x-4$
Thus, the error was made as 3 is multiplied only with $x$ and not with 4.
So, the correct product is,
$3(x-4)=3x-12$