=6,75 giờ +11,2 giờ + 16,8 giờ - 9,8 giờ

=24,95 giờ

a: \(B=\frac12-\left\lbrack\frac38+\left(-\frac74\right)\right\rbrack\)

\(=\frac12-\frac38+\frac74\)

\(=\frac48-\frac38+\frac{14}{8}=\frac{15}{8}\)

b: \(-\frac{4}{12}-\left(-\frac{13}{39}-0,25\right)+0,75\)

\(=-\frac13+\frac13+0,25+0,75\)

=0,25+0,75

=1

c: \(\frac12-\frac13+\frac{1}{23}+\frac16\)

\(=\left(\frac12-\frac13+\frac16\right)+\frac{1}{23}\)

\(=\left(\frac16+\frac16\right)+\frac{1}{23}=\frac13+\frac{1}{23}=\frac{26}{69}\)

d: \(\left(-\frac{13}{7}-\frac49\right)-\left(-\frac{10}{7}-\frac49\right)\)

\(=-\frac{13}{7}-\frac49+\frac{10}{7}+\frac49\)

\(=-\frac{13}{7}+\frac{10}{7}=-\frac37\)

e: \(\left(\frac78-\frac52+\frac47\right)-\left(-\frac37+1-\frac{13}{8}\right)\)

\(=\frac78-\frac52+\frac47+\frac37-1+\frac{13}{8}\)

\(=\frac{20}{8}-\frac52=0\)

f: \(-\frac37+\left(3-\frac34\right)-\left(2,25-\frac{10}{7}\right)\)

\(=-\frac37+3-\frac34-2,25+\frac{10}{7}\)

\(=\frac77+0,75-\frac34\)

=1
g: \(\left(\frac53-\frac37+9\right)-\left(2+\frac57-\frac23\right)+\left(\frac87-\frac43-10\right)\)

\(=\frac53-\frac37+9-2-\frac57+\frac23+\frac87-\frac43-10\)

\(=\left(\frac53+\frac23-\frac43\right)+\left(-\frac37-\frac57+\frac87\right)+\left(9-2-10\right)\)

\(=\frac33+7-10=1-3=-2\)

a, (7,8+4,5) x 3,6

= 12,3 x 3,6 

= 44,28

b, 2,25 + 10 - 4,86 : 1,8

= 2,25 + 10 - 2,7

= 12,25 - 2,7

= 9,55

Chúc bạn học tốt

cảm ơn bn bùi quang anh nhìu ạ

a)317 - 7 . ( X - 53 ) = 100

 7 . ( X - 53 ) = 317 - 100

7 . ( X - 53 ) = 217

X - 53 = 217 : 7

X - 53 = 31

X = 31 + 53

X = 86

b) 

75,75 . X + 2,25 . X + 22 . X  = 100

( 75,75 + 2,25 + 22 ) . X = 100

100 . X =  100

X = 100 : 100

X  =  1

nhớ tích nhiều vào đỗ bảo anh

a) 317-7.(x-53)=100

=) 7.(x-53)=317-100

=) 7.(x-53)=217

=) x-53=217:7

=) x-53=31

=) x=31+53

=) x=84

b) 75,75.x+2,25.x+22.x=100

=) x.(75,75+2,25+22)=100

=) x.100=100

=) x=100:100

=) x= 1

Ko hiểu chỗ nào thì kết bạn với mình mình giảng cho.

11:

a: Số cần tìm là 3;2;1;0

b: 0

10:

\(2\dfrac{1}{2}=2.5>2.25\)

\(6>5\)

nên căn 6>căn 5

-căn 5<0

0<căn 5

=>-căn 5<căn 5

1.tính 

a,2,25+3,75:1,5 = 4,75

b,10-4,86:1,8 = 7,3

a) \(2,25+3,75:1,5\)
\(=2,25+2,5\)
\(=4,75\)
b) \(10-4,86:1,8\)
\(=10-2,7\)
\(=7,3\)

x – 2,25 = 0,75 ⇔ x = 0,75 + 2,25 ⇔ x = 3

\(2^3.\left(2,25-\dfrac{1}{4}\right):\left(\dfrac{10}{3}-1\dfrac{1}{3}\right)^2\\ =8.\left(\dfrac{9}{4}-\dfrac{1}{4}\right):\left(\dfrac{10}{3}-\dfrac{4}{3}\right)^2\\ =8.2:2^2\\ =16:4\\ =4\)

\(B=\left(8-2,25+\dfrac{2}{7}\right)-\left(-6-\dfrac{3}{7}+1\dfrac{1}{4}\right)-\left(3+0,5-1\dfrac{2}{7}\right)\\ B=8-\dfrac{9}{4}+\dfrac{2}{7}+6+\dfrac{3}{7}-\dfrac{5}{4}-3-\dfrac{1}{2}+\dfrac{9}{7}\\ B=\left(8+6-3\right)+\left(-\dfrac{9}{4}-\dfrac{5}{4}\right)+\left(\dfrac{2}{7}+\dfrac{3}{7}+\dfrac{9}{7}\right)-\dfrac{1}{2}\)

\(B=11-\dfrac{7}{2}+2-\dfrac{1}{2}\\ B=\left(11+2\right)+\left(-\dfrac{7}{2}-\dfrac{1}{2}\right)\\ B=13-4\\ B=9.\)