\[\boxed{\mathbf{333.}}\]
\[\textbf{а)}\ 349 + 129 = 478\]
\[285 + 174 = 459\]
\[504 + 237 = 741\]
\[456 + 161 = 617\]
\[678 + 308 = 986\]
\[379 + 470 = 849\]
\[\textbf{б)}\ 175 + 352 - 200 =\]
\[= 175 + 152 = 327\]
\[506 + 248 - 40 = 754 - 40 =\]
\[= 714\]
\[284 + (134 + 30) =\]
\[= 284 + 164 = 448\]