Grade 8 · Year 9 · Class 8 · ages 13–14 · Algebra

Simultaneous equations from a sum and a difference: Grade 8 practice

Finding two numbers from their sum and their difference. Eight questions at a time, instant feedback and a mastery score from 0 to 100.

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The idea in one minute

Add the two equations to get 2x, then divide by 2. Put x back in to find y.

Try these on paper first

One question at each level. Tap a question to see the answer.

Easy x + y = 12 and x − y = 4. Find y.
Answer: 4
Medium x + y = 34 and x − y = 12. Find y.
Answer: 11
Challenge x + y = 16 and x − y = 2. Find x.
Answer: 9

More ways to practise simultaneous equations from a sum and a difference

Printable simultaneous equations from a sum and a difference worksheet with an answer key (new questions every time)
All Grade 8 practice · Algebra worksheets

Related skills

Slope between two points (Grade 8)
Laws of exponents (Grade 8)
Linear functions, finding y (Grade 8)
Equations with x on both sides (Grade 8)

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FAQ

Simultaneous equations from a sum and a difference: questions

What grade is simultaneous equations from a sum and a difference?

It is usually taught in Grade 8 (Year 9 in England, Class 8 in India, ages 13–14), though schools and countries differ. Try the grade above or below if it feels too hard or too easy.

What does a simultaneous equations from a sum and a difference question look like?

For example: "x + y = 34 and x − y = 12. Find y." The answer is 11. Add the two equations to get 2x, then divide by 2. Put x back in to find y.

What should I learn before and after simultaneous equations from a sum and a difference?

Before it, try equations with x on both sides (Grade 8). After it, move on to pythagorean theorem (Grade 8).

How can I get better at simultaneous equations from a sum and a difference?

Add the two equations to get 2x, then divide by 2. Put x back in to find y. Practise a little every day, read the hint after each wrong answer, and use the printable worksheet when you want to write it out.

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