Answer
$2.6$
Work Step by Step
The addends have different signs, so subtract their absolute values and copy the sign of the number with the bigger absolute value.
$|3.4|=3.4
\\|-0.8| = 0.8$
$3.4$ has a higher absolute value, so the sum is positive.
Thus,
$3.4+(-0.8) = |3.4|-|-0.8|=3.4-.8 = 2.6$
