Tính
Helpp 21h nộp
----- Nội dung dịch tự động từ ảnh -----
11) 15(4–7) – 15(5–3)
12) 73(8–59) – 59(8–73)
13) 159(18–59) – 59(18–159)
14) –145(13–57) + 57(10–145)
15) 17(15–16) + 16(17–20)
16) –38(25–4) + 25(–4 + 38)
17) 23(145–17) – 145(23–6)
18) 24(15–4) + 4(24–15)
19) 199(15–17) – 199(–17 + 5)
20) –39(5–99) + 99(10–39)
tổng sau: