JAMB 2018 Mathematics · Question 13

Find the values of x for which x+24\frac {x+2}{4} - 2x−33\frac{2x - 3}{3} < 4

Options

  1. A.x < 8
  2. B.x > -6
  3. C.x < 4
  4. D.x > -3

Answer: B. x > -6

Explanation written with AI and checked against the answer key

To solve this inequality, we need to isolate xx. Here is the step-by-step breakdown:

1. Analyze the inequality

We are given:

x+24−2x−33<4\frac{x+2}{4} - \frac{2x-3}{3} < 4
2. Clear the fractions

To make the calculation easier, find the Least Common Multiple (LCM) of the denominators (4 and 3), which is 12. Multiply every term in the inequality by 12:

12(x+24)−12(2x−33)<12(4)12 \left( \frac{x+2}{4} \right) - 12 \left( \frac{2x-3}{3} \right) < 12(4)

Simplify the fractions:

3(x+2)−4(2x−3)<483(x + 2) - 4(2x - 3) < 48
3. Expand the brackets

Distribute the numbers into the parentheses:

(3x+6)−(8x−12)<48(3x + 6) - (8x - 12) < 48

Be careful with the negative sign when expanding the second bracket:

3x+6−8x+12<483x + 6 - 8x + 12 < 48
4. Simplify and solve for xx

Combine the like terms:

(3x−8x)+(6+12)<48(3x - 8x) + (6 + 12) < 48
−5x+18<48-5x + 18 < 48

Subtract 18 from both sides:

−5x<48−18-5x < 48 - 18
−5x<30-5x < 30

Now, divide both sides by -5. Crucial Rule: When you divide or multiply an inequality by a negative number, you must reverse the inequality sign.

x>30−5x > \frac{30}{-5}
x>−6x > -6
Conclusion

Comparing our result to the given options, we find that x>−6x > -6 matches option B.

Exam Tip: Always remember the "Negative Flip" rule! Whenever you divide or multiply both sides of an inequality by a negative number, immediately flip the sign (e.g., << becomes >>, and vice versa). This is a common trap in JAMB Mathematics questions.

AI can make mistakes. Report anything that looks wrong.

Past questions © the examination body (JAMB/WAEC/NECO). DeeepSolve is not affiliated with them. Rights holders: see /copyright.