Simultaneous equations

Find the pair of numbers that makes two equations true at the same time. About 8 minutes, GCSE.

What you will do

  1. Two equations, two unknowns. With x + y = 10 alone there are many answers. Add x - y = 2 and only one pair works. We solve them together, by making one letter disappear.
  2. Eliminate a letter. Adding the equations cancels y. Watch the whole method.
  3. When the numbers differ. Sometimes we multiply an equation first so a letter matches.
  4. Always check in both. Put your answer into BOTH original equations. A pair that fits only one is not a solution.
  5. Your turn. Find x and y.

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