Giải thích các bước giải:
Ta có:
\(\begin{array}{l}
1,\\
168 - \left( {18 - 2x} \right).12 = 120\\
\Leftrightarrow \left( {18 - 2x} \right).12 = 168 - 120\\
\Leftrightarrow \left( {18 - 2x} \right).12 = 48\\
\Leftrightarrow 18 - 2x = 48:12\\
\Leftrightarrow 18 - 2x = 4\\
\Leftrightarrow 2x = 18 - 4\\
\Leftrightarrow 2x = 14\\
\Leftrightarrow x = 14:2\\
\Leftrightarrow x = 7\\
2,\\
\left[ {75 + \left( {16 - x} \right)} \right].2 = 156\\
\Leftrightarrow 75 + \left( {16 - x} \right) = 156:2\\
\Leftrightarrow 75 + \left( {16 - x} \right) = 78\\
\Leftrightarrow 16 - x = 78 - 75\\
\Leftrightarrow 16 - x = 3\\
\Leftrightarrow x = 16 - 3\\
\Leftrightarrow x = 13\\
3,\\
124 - 24.\left( {3x - 16} \right) = 76\\
\Leftrightarrow 24.\left( {3x - 16} \right) = 124 - 76\\
\Leftrightarrow 24.\left( {3x - 16} \right) = 48\\
\Leftrightarrow 3x - 16 = 48:24\\
\Leftrightarrow 3x - 16 = 2\\
\Leftrightarrow 3x = 16 + 2\\
\Leftrightarrow 3x = 18\\
\Leftrightarrow x = 18:3\\
\Leftrightarrow x = 6\\
4,\\
\left[ {\left( {10 - x} \right).2 + 5} \right]:3 - 2 = 3\\
\Leftrightarrow \left[ {\left( {10 - x} \right).2 + 5} \right]:3 = 3 + 2\\
\Leftrightarrow \left[ {\left( {10 - x} \right).2 + 5} \right]:3 = 5\\
\Leftrightarrow \left( {10 - x} \right).2 + 5 = 3.5\\
\Leftrightarrow \left( {10 - x} \right).2 + 5 = 15\\
\Leftrightarrow \left( {10 - x} \right).2 = 15 - 5\\
\Leftrightarrow \left( {10 - x} \right).2 = 10\\
\Leftrightarrow 10 - x = 10:2\\
\Leftrightarrow 10 - x = 5\\
\Leftrightarrow x = 10 - 5\\
\Leftrightarrow x = 5\\
5,\\
\left[ {80 + \left( {62 - x} \right)} \right]:17 - 7 = 1\\
\Leftrightarrow \left[ {80 + \left( {62 - x} \right)} \right]:17 = 1 + 7\\
\Leftrightarrow \left[ {80 + \left( {62 - x} \right)} \right]:17 = 8\\
\Leftrightarrow 80 + \left( {62 - x} \right) = 17.8\\
\Leftrightarrow 80 + \left( {62 - x} \right) = 136\\
\Leftrightarrow 62 - x = 136 - 80\\
\Leftrightarrow 62 - x = 56\\
\Leftrightarrow x = 62 - 56\\
\Leftrightarrow x = 6\\
6,\\
65 - \left( {5x - 70} \right):2 = 50\\
\Leftrightarrow \left( {5x - 70} \right):2 = 65 - 50\\
\Leftrightarrow \left( {5x - 70} \right):2 = 15\\
\Leftrightarrow 5x - 70 = 15.2\\
\Leftrightarrow 5x - 70 = 30\\
\Leftrightarrow 5x = 30 + 70\\
\Leftrightarrow 5x = 100\\
\Leftrightarrow x = 100:5\\
\Leftrightarrow x = 20\\
7,\\
504:\left( {136 - 2x} \right) + 4 = 32\\
\Leftrightarrow 504:\left( {136 - 2x} \right) = 32 - 4\\
\Leftrightarrow 504:\left( {136 - 2x} \right) = 28\\
\Leftrightarrow 136 - 2x = 504:28\\
\Leftrightarrow 136 - 2x = 18\\
\Leftrightarrow 2x = 136 - 18\\
\Leftrightarrow 2x = 118\\
\Leftrightarrow x = 118:2\\
\Leftrightarrow x = 59
\end{array}\)
\(\begin{array}{l}
8,\\
\left( {13x - 28} \right).15 - {5.2^3} = 320\\
\Leftrightarrow \left( {13x - 28} \right).15 - 5.8 = 320\\
\Leftrightarrow \left( {13x - 28} \right).15 - 40 = 320\\
\Leftrightarrow \left( {13x - 28} \right).15 = 320 + 40\\
\Leftrightarrow \left( {13x - 28} \right).15 = 360\\
\Leftrightarrow 13x - 28 = 360:15\\
\Leftrightarrow 13x - 28 = 24\\
\Leftrightarrow 13x = 28 + 24\\
\Leftrightarrow 13x = 52\\
\Leftrightarrow x = 52:13\\
\Leftrightarrow x = 4
\end{array}\)
