Select the correct combination of mathematical signs to replace * signs and to balance the given equation.
21 * 12 * 4 * 7 = 0
$-$, $\div$, $\times$
$\times$, $\div$, $-$
$\times$, $-$, $\div$
$-$, $\times$, $\div$
Solution
21 $-$ 12 $\div$ 4 $\times$ 7 = 0
21 $-$ 3 $\times$ 7 = 0
21 $-$ 21 = 0