To add the two numbers \(-3.8\) and \(-4.8\), you can simply add their absolute values and keep the negative sign.
\[ |-3.8| + |-4.8| = 3.8 + 4.8 = 8.6 \]
Since both numbers are negative:
\[ -3.8 + -4.8 = -8.6 \]
Therefore, \(-3.8 + -4.8 = -8.6\).