To find x, undo what was done to it. Do the same thing to both sides to keep them equal. 3x + 5 = 20. Take 5 from both sides: 3x = 15. Divide both sides by 3: x = 5.
Worked example
Solve for x: 1 + x = 2.
Answer:x = 1
First simplify each side (use the distributive property and combine like terms): the left side is x + 1 and the right side is 2. Get the x terms together: x = 1. Divide both sides by 1: x = 1. Answer: x = 1.
For grown-ups: Multi-step linear equations; no / one / infinitely many solutions. Below: three problems to try with the worked answers, and a free printable sheet. Children can practise the same skill as a game, with no sign-up and no ads.
CCSS 8.EE.C.7
What this practises, for teachers
Practices multi-step linear equations; no / one / infinitely many solutions (8.EE.C.7). A printable sheet with its answer key, worked answers on the page, no accounts.
First simplify each side (use the distributive property and combine like terms): the left side is 2x and the right side is 4. Get the x terms together: 2x = 4. Divide both sides by 2: x = 2. Answer: x = 2.
Solve for x: 9x − 4 = 23.
Show the answer and how
Answer:x = 3
First simplify each side (use the distributive property and combine like terms): the left side is 9x − 4 and the right side is 23. Get the x terms together: 9x = 27. Divide both sides by 9: x = 3. Answer: x = 3.
Solve for x: 6x − 11 = 1.
Show the answer and how
Answer:x = 2
First simplify each side (use the distributive property and combine like terms): the left side is 6x − 11 and the right side is 1. Get the x terms together: 6x = 12. Divide both sides by 6: x = 2. Answer: x = 2.