Answer
$-1$
Work Step by Step
In adding two numbers with the same sign, perform the following steps:
(1) Add their absolute values.
$|-\frac{7}{10}| + |-\frac{3}{10}| = \frac{7}{10} + \frac{3}{10} = \frac{10}{10}=1$
(2) The sum must have sign common to the addends.
$-\frac{7}{10}+(-\frac{3}{10}) = -1$
Thus, the sum is $-1$.
