\(\frac{72+36\times2+24\times3+18\times4+12\times6+168}{2+2+4+6+10+.....+60}\)

\(=\frac{72+72+72+72+72+168}{\left(68-2\right):2+1}\)

\(=\frac{72\times5+168}{\left(68+2\right)\times34\div2}\)

\(=\frac{360+168}{1190}=\frac{528}{1190}=\frac{264}{595}\)

\(b\frac{1991\times1993-1}{1990+1991\times1992}\)

\(=\frac{1991\times\left(1993-1\right)-1}{1990+1991\times1990}\)

\(=\frac{1991\times1992-1}{1990+1991\times1992}\)

\(=\frac{1990}{1990}=1\)

-168 + ( + 72 ) . ( - 168 ) + ( - 168 ) . ( + 27 )

= - 168 . 1 + 72 . ( - 168 ) + ( - 168 ) . 27

= - 168 . ( 1 + 72 + 27 )

= - 168 . 100

= - 16800

 ( -168 ) + 72 x ( -168 ) + ( -168 ) x 27 

=  ....

k mình

k lại

72+36.2+24.3+18.4+12.6+144

=72+72+72+72+72+72.2

=72.5+72.2

=72.(5+2)

=72.7

=504

72+36.2+24.3+18.4+12.6+144

=72+72+72+72+72+72.2

=72.5+72.2

=72.(5+2)

=72.7

=504

72+36*2+24*3+18*4+12*6+168

=72+72+72+72+72+168

=72*5+168

=360+168

=528

72+72+72+72+72+168=72*5+168=360+168=528

72 + 36 * 2 + 24 * 3 + 18 * 4 + 12 + 6 + 168

= 72 + 72 + 72 + 72 + 12 + 6 + 168

= 72 * 4 + 12 + 6 + 168

= 288 + 12 + 6 + 168

= 474

Chúc bạn học tốt! ^_^

72+36x2+24x3+18x4+12+6+168

=72+72+72+72+12+6+168

=474

=72+76+72+72+72+168=72x4+76+168=550

550 đó