How do you go about rearranging equations where the required subject appears on both sides? Such as making x the subject of 7x + a = 3x + b.

To rearrange any equation, you must always do the same to both sides.
If you take a number from one side, you must also take it from the other. If you divide a side by one number you must divide the other by the same number (and this applies to the whole of both sides, not just part of the side).

7x + a = 3x + b, make x the subject:
Begin by collecting like terms on each side (so all the terms involving x on one side, and all the other terms on the other side).

  1. Take 3x from both sides:
    7x + a - 3x = 3x + b - 3x
    4x + a = b
  2. Take a from both sides:
    4x + a - a = b - a
    4x = b - a
  3. Divide both sides by 4 (as x must be alone):
    (4x)/4 = (b - a)/4
    x = (b - a)/4 This is our answer

RT
Answered by Rachael T. Maths tutor

20595 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

How do I solve a simultaneous equation like this: 2x-5y=3, 3x+2y=14 ?


Solve the simultaneous equations. 2x + y = 18, x−y=6


5y + 1 = 3y + 13


10 girls and 15 boys sit a test. The mean mark for the boys is 70. The mean mark for girls is 82. Work out the mean mark for the whole class.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences