\[Страница\ 52.\]
\[\boxed{\mathbf{1.}}\]
\[2 \cdot 6 + 2 = 2 \cdot 7 = 2 \cdot 8 - 2\]
\[18 + 18 + 18 = 18 \cdot 3 = 3 \cdot 18\]
\[3 \cdot 9 - 3 = 3 \cdot 7 + 3\]
\[\boxed{\mathbf{2.}}\]
\[4 \cdot 31 > 13 \cdot 4\]
\[28 \cdot 2 < 28 \cdot 3\]
\[14 - 2 > 14\ :2\]
\[16 \cdot 4 > 16 + 4\]
\[32 \cdot 2 = 2 \cdot 32\]
\[12 \cdot 2 > 12\ :2\]
\[\boxed{\mathbf{3.}}\]
\[15 - 6 + 9 = 18\]
\[13 + 5 - 9 = 9\]
\[11 + 4 - 7 = 8\]
\[36 - 12 = 24\]
\[38 - 38 = 0\]
\[90 - 1 = 89\]
\[53 + 7 = 60\]
\[47 - 7 = 40\]
\[11 + 9 = 20\]
\[\boxed{\mathbf{4.}}\]
\[36 - a > 36 - 4\]
\[a = 0;1;2;3.\]