B

B

B

mình làm ý a hen

25-(30-7)+75-47

=25-(30-7)+28

=25-23+28

=2+28

=30

\(25-\left(30-7\right)+75-47\)

\(=25-30+7+75-47\)

\(=30\)

\(\left(-54-91\right)-\left(59-74\right)\)

\(=-54-91-59+74\)

\(=-130\)

câu kia tương tự nha

Chọn đáp án B

Theo tính chất dãy tỉ số bằng nhau ta có :

\(\frac{a}{2}=\frac{b}{3}=\frac{c}{5}=\frac{2a}{2.2}=\frac{b}{3}=\frac{3c}{3.5}=\frac{2a+b-3c}{4+3-15}=\frac{64}{-8}=-8\)

\(\frac{a}{2}=-8\Rightarrow a=\left(-8\right).2=-16\)

\(\frac{b}{3}=-8\Rightarrow b=\left(-8\right).3=-24\)

\(\frac{c}{5}=-8\Rightarrow c=\left(-8\right).5=-40\)

Vậy a=-16 ; b=-24 và c=-40

ai giúp với khẩn cấp !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

ĐẶT a/2=b/3=c/5=k

=> a=2k

     b=3k

     c=5k

có 2a+b-c3=64

=> k.2.2+3k-k.3.5=64

=> k.4+3k+k15=64

=> k(3+4+15)=64

=> k.22=64 

=> k=64/22

hình như bạn chép sai đề bài

k nếu xem cách mk hiểu nha

According to Dr. B. J. Casey from the Weill Medical College of Cornell University, teens are very quick and accurate in (56) __________ judgments and decisions on their own and in situations (57) __________ they have time to think. (58) __________, when they have to make decisions in the heat of the moment or in social situations, their decisions are often influenced by external (59) __________ like peers. In a study funded by the National Institute on Drug Abuse (NIDA), teen volunteers played a video driving game, (60) __________ alone or with friends watching. (61) __________ the researchers discovered was that the number of risks teens (62) __________ in the driving game more than doubled when their friends were watching as (63) __________ to when the teens played the game alone. This outcome (64) __________ that teens may find (65) __________ to control impulsive or risky behaviors when their friends are around, or in situations that are emotionally charged.

56. A. doing B. getting C. making D. giving

57. A. where B. when C. what D. which

58. A. Moreover B. Although C. Therefore D. However

59. A. aspects B. factors C. elements D. setting

60. A either B. both C. neither D. whether

61. A. Which B. This C. What D. How

62. A. made B. did C. took D. perfomed

63. A. comparing B. comparison C. compare D. compared

64. A. realizes B. indicates C. tells D. describes

65. A is more difficult B. more difficult it is C. more difficult D. it more difficult

56.C

57.A

58.D

59.B

60.A

61.C

62.C

63.D

64.B

65.D

Tổng 3 số là : 

             ( 64 + 61 + 65 ) : 2 = 95

Số A là :

             95 - 61 = 34

Số B là :

             95 - 65 = 30

Số C là :

            95 - 64 = 31

                 Đáp số : A = 34 ; B = 30 ; C = 31.

Chúc em học tốt.