Question

Which of the following equations cannot be formed using the equation x = 7?

(a) $2x+1=15$

(b) $7x-1=50$

(c) $x-3=4$

(d) $\frac{x}{7}-1=0$

• A. (a)
• B. (b)
• C. ( c )
• D. (d)

Answer 1

The correct option is B

(b)

Explanation for the correct option:

Option (b): Consider $7x-1=50$.

$\begin{array}{rcl}7x-1& =& 50\\ & \Rightarrow & 7x=51\\ & \Rightarrow & x=\frac{51}{7}\end{array}$

Hence, option (b) is correct.

Explanation for the incorrect options:

Option (a): Consider $2x+1=15$.

$\begin{array}{rcl}2x+1& =& 15\\ & \Rightarrow & 2x=14\\ & \Rightarrow & x=7\end{array}$

Therefore, option (a) is incorrect.

Option (c): Consider $x-3=4$.

$\begin{array}{rcl}x-3& =& 4\\ & \Rightarrow & x=7\end{array}$

Therefore, option (c) is incorrect.

Option (d): Consider $\frac{x}{7}-1=0$.

$\begin{array}{rcl}\frac{x}{7}-1& =& 0\\ & \Rightarrow & \frac{x}{7}=1\\ & \Rightarrow & x=7\end{array}$

Therefore, option (d) is incorrect.

Thus, options (a), (c), and (d) are incorrect.

Hence, option (b) is correct.