Unknowns on both sides
When the letter appears on both sides, first move the letter terms to one side, then solve as normal.
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Analogy
Like two teams on a see-saw: take the same number of players off each side until one side has none.
Example
Take 2x from both sides: 3x - 3 = 9Add 3: 3x = 12Divide by 3: x = 4
In practice
Comparing two phone plans with different fixed fees and prices per minute gives an equation with x on both sides.
Practice
Flashcards
- Solve 5x - 3 = 2x + 9.x = 4. Subtract 2x, add 3, divide by 3.
Questions people ask
Which side should the x terms go on?
Either side works. Many people move them to the side where x has the larger number, so the answer stays positive. For 5x - 3 = 2x + 9, subtracting 2x leaves 3x on the left. Both choices give the same final answer.
What if the equation has brackets?
Expand the brackets first, then collect the letter terms. For 2(x + 3) = x + 10, expanding gives 2x + 6 = x + 10. Take x from both sides: x + 6 = 10, so x = 4.