If 5x - 3 = 4x - 7, what is the value 6x?

Analyze the question: We have a linear equation in x. We must first find x, then multiply it by 6 to get the value of 6x.

Concept: To solve a linear equation, collect the x-terms on one side and the numbers on the other side. Whatever you do to one side, do to the other.

Solution:

5x - 3 = 4x - 7

Subtract 4x from both sides: 5x - 4x - 3 = -7 x - 3 = -7

Add 3 to both sides: x = -7 + 3 x = -4

Now find 6x: 6x = 6 × (-4) = -24

Check: Put x = -4 back into the original equation.

• Left side: 5(-4) - 3 = -20 - 3 = -23
• Right side: 4(-4) - 7 = -16 - 7 = -23

Both sides are equal, so x = -4 is correct.

Answer: E (-24)

Exam tip: Read the final line of the question carefully. The question asks for 6x, not x. Many students stop at x = -4 and wrongly choose D. Always check what the question is asking for before you pick an option.