\(\text{a) -72+ (154+76) }\)

\(=-72+230\)

\(=158\)

\(\text{b) (144-97) -144 }\)

\(=47-144\)

\(=-97\)

\(\text{c) -145- (-18-145) }\)

\(=-145-\left(-163\right)\)

\(=18\)

\(\text{d) 38-(12+13+14) }\)

\(=38-39=-1\)

\(\text{e)-144-(29-144-144) }\)

\(=-144-\left(-259\right)=115\)

\(-72+\left(154+74\right)\)

\(=\left(-72\right)+230\)

\(158\)

\(\left(144-97\right)-144\)

\(=47-144\)

\(=-97\)

\(-145-\left(-18-145\right)\)

\(=\left(-145\right)-\left(-163\right)\)

\(=18\)

\(38-\left(12+13+14\right)\)

\(=38-39\)

\(=-1\)

\(-144-\left(19-144-144\right)\)

\(=\left(-144\right)-\left(-259\right)\)

\(=115\)

Bài 1 : Tính nhẩm 

a) 18 : 2 = 9                    c) 60 : 10 = 6

b) 12 : 4 = 3                d) 100 : 2 = 50

Bài 2 : Đặt tính rồi tính 

323 + 257 = 600           589 + 120 = 709                    710 + 97 = 807                    138 + 45 = 183

Bài 3 : > , < , = 

326 + 590 > 197 + 612                  197 + 107 < 81 + 610                 

345 + 555 = 555 + 345

_HT_

Bài 1 : Tính nhẩm 

a) 18 : 2 =   9                  c) 60 : 10 = 6

b) 12 : 4 =  3                   d) 100 : 2 = 50

Bài 2 : Đặt tính rồi tính 

323 + 257   =600           589 + 120      =709                    710 + 97 =807                         138 + 45=183

Bài 3 : > , < , = 

326 + 590 .>.. 197 + 612                  197 + 107 .<.. 81 + 610                       345 + 555 ...= 555 + 345

a: \(\frac{60}{72}=\frac{60:12}{72:12}=\frac56\)

\(\frac{24}{36}=\frac{24:12}{36:12}=\frac23=\frac{2\times2}{3\times2}=\frac46\)

mà 5>4

nên \(\frac{60}{72}>\frac{24}{36}\)

b: \(\frac{-13}{18}=\frac{-13\times2}{18\times2}=\frac{-26}{36}\)

\(\frac{-7}{12}=\frac{-7\times3}{12\times3}=\frac{-21}{36}\)

mà -26<-21

nên \(-\frac{13}{18}<-\frac{7}{12}\)

c: \(\frac{4}{15}=\frac{4\times6}{15\times6}=\frac{24}{90}\)

\(\frac{7}{18}=\frac{7\times5}{18\times5}=\frac{35}{90}\)

mà 24<35

nên \(\frac{4}{15}<\frac{7}{18}\)

d: \(\frac{123}{321}>0;0>-\frac{312}{213}\)

Do đó: \(\frac{123}{321}>-\frac{312}{213}\)

a: \(\frac{60}{72}=\frac{60:12}{72:12}=\frac56\)

\(\frac{24}{36}=\frac{24:12}{36:12}=\frac23=\frac{2\times2}{3\times2}=\frac46\)

mà 5>4

nên \(\frac{60}{72}>\frac{24}{36}\)

b: \(\frac{-13}{18}=\frac{-13\times2}{18\times2}=\frac{-26}{36}\)

\(\frac{-7}{12}=\frac{-7\times3}{12\times3}=\frac{-21}{36}\)

mà -26<-21

nên \(-\frac{13}{18}<-\frac{7}{12}\)

c: \(\frac{4}{15}=\frac{4\times6}{15\times6}=\frac{24}{90}\)

\(\frac{7}{18}=\frac{7\times5}{18\times5}=\frac{35}{90}\)

mà 24<35

nên \(\frac{4}{15}<\frac{7}{18}\)

d: \(\frac{123}{321}>0;0>-\frac{312}{213}\)

Do đó: \(\frac{123}{321}>-\frac{312}{213}\)

Cau 1)

21+(x+23)=50

X+23=50-21

X=29-23

X=6

Cau 2)

125+(x-100)=150

X-100=150-125

X=25+100

X=125

b) (24+72).(36+60):12=96.2:12

=192:12

=16

a)27+45+18+81

=3.9+5.9+2.9+9.9

=(3+5+2+9)9

=19.9=171

b)(24+72+36+60):12

=24:12+72:12+36:12+60:12

=2+6+3+5=16

- 84

- 25

= -84
= -25

A 50

b 97

c 74

k cho mình nhé