$\color{black}{\text{a)x+252=453+325}}$
$\color{black}{\text{x+252=778}}$
$\color{black}{\text{x=778-252}}$
$\color{black}{\text{x=526}}$
$\color{black}{\text{b)x-642=986-754}}$
$\color{black}{\text{x-642=232}}$
$\color{black}{\text{x=232+642}}$
$\color{black}{\text{x=874}}$
