7 3 − x ∗ 3 2 x − 3 = 21 {\displaystyle 7^{3-x}*3^{2x-3}=21}
7 3 − x ∗ 3 2 x − 3 = 21 7 3 − x ∗ 3 2 x − 3 = 3 ∗ 7 3 − x = 1 2 x − 3 = 1 x = 2 x = 2 {\displaystyle {\begin{aligned}7^{3-x}*3^{2x-3}=21\\7^{3-x}*3^{2x-3}=3*7\\3-x=1\ \ \ 2x-3=1\\x=2\ \ \ x=2\end{aligned}}}