199 + 33 + 199 + 44 + 199 = 674 

199+33+199+44+199

=(199x3)+(33+44)

=597+77

=674

k mik nha!^_^
:3)))

Số cần tìm là:

199+33+199+44+199= 674

Đáp số: 674

=199x3+199x7

=199x(3+7)

=199x10

=1990

hok tốt

= 199 x ( 3 + 7 )

= 199 x 10

= 1990

 199 + 199 + 199 + 199 x 7

=  199 x 1 + 199 x 1 + 199 x 1 + 199 x 7

= 199 x ( 1 + 1 + 1 + 7 )

= 199 x 10

= 1990

 Hok tốt

\(\frac{5}{14}\frac{5}{14}\) LÀ NHÂN À

Mình lỡ đánh nhầm 2 lần \(\frac{5}{14}\)nha :)) chỉ 1 lần thôi

\(\frac{x-199}{6}+\frac{x-199}{12}+\frac{x-199}{20}+\frac{x-199}{30}+\frac{x-199}{42}=\frac{5}{14}\)

\(\left(x-199\right)\left(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\right)=\frac{5}{14}\)

\(\left(x-199\right)\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\right)=\frac{5}{14}\)

\(\left(x-199\right)\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{6}-\frac{1}{7}=\frac{5}{14}\right)\)

\(\left(x-199\right)\left(\frac{1}{2}-\frac{1}{7}\right)=\frac{5}{14}\)

\(\left(x-199\right).\frac{5}{14}=\frac{5}{14}\)

\(\Leftrightarrow x-199=1\)

\(\Leftrightarrow x=200\)

\(199^3-199=199.\left(199^2-1\right)=199.\left(199+1\right).\left(199-1\right)=199.200.198⋮200\left(đpcm\right)\)

\(199^3-199=199\left(199^2-1\right)=199\left(199+1\right)\left(199-1\right)=199.200.198⋮200\left(đpcm\right)\)

\(199^3-199\\=199(199^2-1)\\=199(199-1)(199+1)\\=199\cdot198\cdot200\)

Vì \(199\cdot198\cdot200⋮200\) nên \(199^3-199⋮200\)

Bắn tung tóe

a.11/7.8/13+8/13.3/7+8/13

=8/13.(11/7+3/7+1)

=8/13.3

=24/13

b.5/7.8/13+8/13.9/7-8/13

=8/13.(5/7+9/7-1)

=8/13.1

=8/13

c.157.199-56.199-199

=199.(157-56-1)

=199.100

19900

-(2012-199+20)-(-199+20)

=-2012+199-20+199-20

=-2012+(200-1)-20+(200-1)-20

=-2012+200+200-1-1-20-20

=-2012+(200+200)-(20+20+1+1)

=-2012+400-42

=-1612-42=-1654