Resuelve las siguientes los siguientes ejercicios a)(+3)+(+21) + (-15) =
b)(-5) + (+7)+(- 12) =
c)(+14) + (-9) + (-7)=
d)+13-5 + 4 -11 -6 -11 - 4 + 45
=
e)+9-5 + 11 - 12 + 14 =​

por favor

alot

step-by-step explanation:

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in problems involving proportions, we can use cross products to test whether two ratios are equal and form a proportion. to find the cross products of a proportion, we multiply the outer terms, called the extremes, and the middle terms, called the means.

hope it