Tính bằng cách hợp lý

Tính hợp lý
1) (–12) +6.(–3)
2) (36 -2020) + (2019 -136) – 27
3) (144 – 97) – (244 – 197)
4) (–24).13 – 24.( –3)
5) <!--[if gte msEquation 12]>54+55+56+57+58-(64+65+66+67+68)<!--[endif]--><!--[if gte vml 1]--> <!--[endif]-->6) 24(16 – 5) – 16(24 – 5)
<!--[if gte msEquation 12]> 7) <!--[endif]--><!--[if gte vml 1]--> <!--[endif]-->47.(23 + 50) – 23.(47 + 50)