How do you evaluate #30+ ( - 6) + ( - 28) + 7#?

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Answer 1 · 2017-09-02T23:13:52

See a solution process below:

Execute the Addition operations from left to right:

#color(red)(30) + (color(red)(-6)) + (-28) + 7 =>#

#color(red)(30) - (color(red)(6)) + (-28) + 7 =>#

#color(red)(24) + (color(red)(-28)) + 7 =>#

#color(red)(24) - color(red)(28) + 7 =>#

#color(red)(-4) + color(red)(7) =>#

#3#

Answer 2 · 2017-09-03T08:19:49

#30+(-6)+(-28)+7#

#=3#

Students often add positive and negative numbers together incorrectly, because they add incorrect numbers together before subtracting.

Because of the commutative law #" "(a+b =b+a)#,
you can change the order of terms in an expressions.

However, THE SIGNS OF THE TERMS STAY THE SAME!

A way to avoid errors is to write an expression with all the positives at the beginning and the negatives at the end.

#30+(-6)+(-28)+7#

#=color(blue)(30+7)+color(red)((-6)+(-28))#

#=color(blue)(37) + (color(red)(-34))" "larr# there are more positives

#=color(blue)(3)#