-2x - 40 = (5 - x) - (-15 + 60)
-2x - 40 = (5 - x) - 45
-2x - 40 = -40 - x
-2x - x = 40 - 40
-3x = 0
x = 0
2(x - 4) - 3(x + 7) = 14
2x - 8 - 3x - 21 = 14
-x - 29 = 14
-x = 14 + 29
-x = 43
x = -43
-7(5 - x) - 2(x - 10) = 15
-35 + 7x - 2x + 20 = 15
-15 + 5x = 15
5x = 15 + 15
5x = 30
x = 6
\(-2x-40=\left(5-x\right)-\left(-15+60\right)\)
\(\Leftrightarrow\)\(-2x-40=5-x+15-60\)
\(\Leftrightarrow\)\(-2x-40=-x-40\)
\(\Leftrightarrow\)\(-2x+x=40-40\)
\(\Leftrightarrow\)\(x=0\)
Vậy....
\(x+18=2-2x\)
\(2x+x=2-18\)
\(3x=-20\)
\(x=-20:3\)
\(x=\frac{-20}{3}\)
−2x−40=(5−x)−(−15+60)
⇔−2x−40=5−x+15−60
⇔−2x−40=−x−40
⇔−2x+x=40−40
⇔x=0