7.x - x = 521 : 519 + 3.22 - 70
=> x(7 - 1) = 52 + 3.4 - 1
=> 6x = 25 + 12 - 1
=> 6x = 36
=>x = 36 : 6
=> x = 6
vậy_
\(7x-x=5^{21}:5^{19}+3\times2^2-7^0\)
\(\Rightarrow\left(7-1\right)x=5^2+3\times4-1\)
\(\Rightarrow6x=25+12-1\)
\(\Rightarrow6x=37-1\)
\(\Rightarrow6x=36\)
\(\Rightarrow x=36:6\)
\(\Rightarrow x=6\)
Vậy x = 6
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