silemus.
← All examples
  1. 1Adding 2/3 + 3/4
  2. 2Subtracting fractions
  3. 3Multiplying fractions
  4. 4Dividing fractions
  5. 5Fraction of a number
  6. 6Multiplying decimals
  7. 7Dividing by a decimal
  8. 8Finding 15% of 240
  9. 9Percent increase
  10. 10Finding a sale price
  11. 11Finding original price before discount
  12. 12Sharing $120 in a ratio
  13. 13Unit rate, proportions
  14. 14Speed from distance and time
  15. 15Price per ounce, unit rate
  16. 16Order of operations
  17. 17Order of operations
  18. 18Order of operations, integers
  19. 19Adding and subtracting integers
  20. 20Solving x/4=9
  21. 21Solving 3x−7=20
  22. 22Solving 5−2x=17
  23. 23Solving 4x+3=2x+15
  24. 24Area and perimeter of rectangle
  25. 25Area of a triangle
  26. 26Area of a circle
  27. 27Circumference of a circle
  28. 28Area and perimeter, L-shape
  29. 29Area of rectangle plus semicircle
  30. 30Angle sum of a triangle
  31. 31Angles on a straight line
  32. 32Base angles of isosceles triangle
  33. 33Mean of a data set
  34. 34Median and mode
  35. 35Mean of five scores
  36. 36Probability of one outcome
  37. 37Probability of independent events

21Solving 3x−7=20

Solve 3x − 7 = 20.

Undo what's attached to x in reverse order: add 7 to both sides to get 3x = 27, then divide by 3 to get x = 9. Check: 3·9 − 7 = 20.

How good is this answer?