What is rational number? The definition of rational number

What is rational number? The definition of rational number

Mathematically, a rational number is the ratio of an integer a to a non-zero integer B, for example, 3 / 8, generally a / B, so it is also called a fraction
A rational number is a set of integers and fractions
The fractional part of a rational number is finite or circular. Real numbers that are not rational numbers are called irrational numbers

Play the 24 point game with -- 5,3,7, - 12 to mix these numbers

There are 30 algorithms for 24 point game title [- 5,3,7, - 12]
1. -12－[3×﹙-5－7﹚]
2. ﹙3＋7﹚÷﹙-5÷-12﹚
3. -5－[7＋﹙-12×3﹚]
4. -5－[﹙3×-12﹚＋7]
5. [﹙7＋3﹚×-12]÷-5
6. ﹙-12÷-5﹚×﹙7＋3﹚
7. ﹙7＋3﹚×﹙-12÷-5﹚
8. [3×﹙7－-5﹚]＋-12
9. -12÷[-5÷﹙7＋3﹚]
10. -12＋[﹙7－-5﹚×3]
11. [-12×﹙3＋7﹚]÷-5
12. [-5－﹙-12×3﹚]－7
13. [-12×﹙7＋3﹚]÷-5
14. ﹙3＋7﹚×﹙-12÷-5﹚
15. ﹙-5－7﹚－﹙-12×3﹚
16. ﹙7＋3﹚÷﹙-5÷-12﹚
17. ﹙-12÷-5﹚×﹙3＋7﹚
18. [﹙3＋7﹚÷-5]×-12
19. -12＋[3×﹙7－-5﹚]
20. ﹙-5－7﹚－﹙3×-12﹚
21. [﹙7＋3﹚÷-5]×-12
22. -12－[﹙-5－7﹚×3]
23. [﹙3＋7﹚×-12]÷-5
24. [﹙7－-5﹚×3]＋-12
25. [-5－﹙3×-12﹚]－7
26. -12×[﹙3＋7﹚÷-5]
27. -12×[﹙7＋3﹚÷-5]
28. -12÷[-5÷﹙3＋7﹚]
29. -5－[﹙-12×3﹚＋7]
30. -5－[7＋﹙3×-12﹚]

The addition and subtraction of integers: first simplify, then evaluate
15a²－﹛－4a²＋[5a－8a²－﹙2a²－a﹚]＋9a²－3a﹜
Where a = - - 189;

15a²－﹛－4a²＋[5a－8a²－﹙2a²－a﹚]＋9a²－3a﹜=15a²-﹛－4a²＋6a－10a²＋9a²－3a﹜=15a²-﹛－5a²+3a﹜=20a²-3aa=-1/220a²-3a=13/2...