Explain what is wrong with each of the following:
(a) $3 \cdot 2^{2} \stackrel{?}{=} 6^{2} \stackrel{?}{=} 36$
(b) $3 x^{4} \stackrel{?}{=} 3 x \cdot 3 x \cdot 3 x \cdot 3 x$
(c) $5^{4} \cdot 2 \stackrel{?}{=} 20 \cdot 2 \stackrel{?}{=}40$
(d) $\left(3 x^{3}\right)^{2} \stackrel{?}{=} 6 x^{6}$
(e) $-3^{4} \stackrel{?}{=}(-3) \cdot(-3) \cdot(-3)(-3) \stackrel{?}{=} 81$
(f) $x^{4}+x^{5} \stackrel{?}{=} x^{9}$
(g) $x^{2} \cdot x^{7} \stackrel{?}{=} x^{14}$
(h) $\left(x^{2}\right)^{4} \stackrel{?}{=} x^{6}$