\[\boxed{\mathbf{345.}}\]
\[\textbf{а)}\ 536 + 154 = 690\]
\[463 + 278 = 741\]
\[364 + 52 = 416\]
\[271 + 529 = 800\]
\[734 + 128 = 862\]
\[653 + 347 = 1000\]
\[\textbf{б)}\ 287 + (963 - 500) =\]
\[= 287 + 463 = 950\]
\[753 - 50 + 197 = 703 + 197 =\]
\[= 900\]
\[800 - (467 + 2) = 800 - 469 =\]
\[= 331\]