\[\boxed{\mathbf{3.}\mathbf{318}}\]
\[\textbf{а)}\ 90 - 16 = 74\ :2 = 37 + 23 =\]
\[= 60\ :5 = 12\]
\[\textbf{б)}\ 50 + 19 = 69\ :3 = 23 + 47 =\]
\[= 70\ :5 = 14\]
\[\textbf{в)}\ 42 + 26 = 68\ :2 = 34 - 16 =\]
\[= 18 \cdot 3 = 54\]
\[\textbf{г)}\ 60 - 22 = 38\ :2 = 19 + 46 =\]
\[= 65\ :5 = 13\]
\[\textbf{д)}\ 70 - 19 = 51\ :3 = 17 + 13 =\]
\[= 30 \cdot 5 = 150\]