\[\boxed{\mathbf{225.}}\]
\[\textbf{а)}\ 50 + 234 = 284\]
\[651 - 30 = 621\]
\[480 + 20 = 500\]
\[344 - 2 \cdot 2 = 344 - 4 = 340\]
\[160 + 15\ :3 = 160 + 5 = 165\]
\[540 - 5 \cdot 4 = 540 - 20 = 520\]
\[\textbf{б)}\ 848 - 40\ :5 = 848 - 8 =\]
\[= 840\]
\[7 \cdot 6 + 300 = 42 + 300 = 342\]
\[860 + 4 \cdot 10 = 860 + 40 = 900\]