30 + 12 + ( - 20 ) + ( - 12 )
= 30 + 12 - 20 - 12
= 42 - 20 - 12
= 22 - 12
= 10
30 + 12 + (-20) + (-12) = 10
(-17) + 5 + 8 + 17 = 13
10
13
ai tk mk
mk tk lại
mk hứa
thank you
a ) 30 + 12 + ( - 20 ) + ( - 12 )
= [ 30 + ( - 20 ) ] + [ 12 + ( - 12 ) ]
= 10 + 0
= 10
b ) ( - 17 ) + 5 + 8 + 17
= ( 5 + 8 ) + [ ( - 17 ) + 17 ]
= 13 + 0
= 13