Which of the following equations cannot be formed using the equation \(x = 7\)?
2x + 1 = 15
7x - 1 = 50
x - 3 = 4
\(\dfrac{x}{7} - 1 = 0\)
If \(x = 7\):
\(7x - 1 = 7(7) - 1 = 49 - 1 = 48\), not 50. Hence option (b) is invalid.