The additive inverse of $6-\left(-4\right)$ is 

Find the value of $x$.

$-1256+x=-742$

Simplify:

$\left[823+\left(-398\right)\right]+\left[413-312+\left(-400\right)\right]-\left(-30\right)+286-\left\{\left(-115+117\right)\right\}$

Find the greatest integer that could replace the $x$ in order to make the sentence true.

$\left|-28\right|+\left|85-16\right|-\left|x\right|=4$