The additive inverse of a is denoted by unary minus: −a (see also § Relation to subtraction below). For example, the additive inverse of 7 is −7, because 7 + (−7) = 0, and the additive inverse of −0.3 is 0.3, because −0.3 + 0.3 = 0
To find out how much is needed for 1 you will need to divide each given value by 4:
12 marshmallows / 4 = 3
8 graham crackers / 4 = 2
4 smores / 4 = 1
you then need to multiply each value by 3 :
3 marshmallows x 3 = 9
2 graham crackers x 3 = 6
1 smore x 3 = 3
therefore the answer would be :
9 marshmallows
6 graham crackers
hope this helps you
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as a mixed number would be

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