4.解答
$$ \begin{eqnarray}
(1)&:&15-7&-&4 \\
&=& 8 &-& 4 \\
&=& 4\\ \\
(2)&:&12+4&-&8\\
&=& 16&-&8 \\
&=& 8\\ \\
(3)&:&4 \times 3 &\times& 3 \\
&=& 12 &\times& 3 \\
&=& 36\\ \\
(4)&:&18 \div 3 &\times& 2\\
&=& 6 &\times& 2 \\
&=& 12 \\ \\
(5)&:&3&+&15\div3 \\
&=& 3&+&5 \\
&=& 8 \\ \\
(6)&:&6 \times 2 &-& 7 \\
&=& 12 &-& 7 \\
&=& 5\\ \\
(7)&:&(7-4)&\times&7 \\
&=& 3 &\times& 7 \\
&=& 21\\ \\
(8)&:&22&-&4\times 4&+&3 \\
&=& 22&-&16&+&3 \\
&=& 6&& &+&3 \\
&=& 9\\ \\
(9)&:&13&+&32\div&(2\times 4)& \\
&=& 13&+&32\div&8& \\
&=& 13&+&4 \\
&=&17 \\ \\
(10)&:& 6 &+&2^3 \\
&=& 6 &+& 2\times 2 \times 2 \\
&=& 6 &+& 8 \\
&=& 14 \\ \\
(11) &:& 2^3 &\times& 3^2 \\
&=& 2\times 2 \times 2 &\times& 3 \times 3 \\
&=& 8 & \times 9 \\
&=& 72 \\ \\
(12)&:&(4^2&-&1)&\div& 3 \\
&=& (4\times 4 &-&1)&\div& 3\\
&=& (16 &-&1)&\div&3 \\
&=& 15 && &\div& 3 \\
&=& 5\\
\end{eqnarray}$$