a: 5+2x=20-3x
=>2x+3x=20-5
=>5x=15
=>\(x=\dfrac{15}{5}=3\)
b: \(7-\left(2x+4\right)=-\left(x+4\right)\)
=>7-2x-4=-x-4
=>-2x+7=-x
=>-x=-7
=>x=7
c: \(\left(5x+2\right)-3\left(2x+1\right)=-3x+7\)
=>5x+2-6x-3=-3x+7
=>-3x+7=-x-1
=>-2x=-8
=>x=4
d: \(2x-\left(3-5x\right)=4\left(x+3\right)\)
=>2x-3+5x=4x+12
=>7x-3=4x+12
=>3x=15
=>\(x=\dfrac{15}{3}=5\)
e: \(5\left(2x-3\right)-4\left(5x-7\right)=19-2\left(x+11\right)\)
=>10x-15-20x+28=19-2x-22
=>-10x+13=-2x-3
=>-8x=-16
=>\(x=\dfrac{-16}{-8}=2\)
f: \(x^2-\left(x+2\right)\left(x-2\right)=2x\)
=>\(x^2-\left(x^2-4\right)=2x\)
=>2x=4
=>x=2
g: \(\dfrac{1-3x}{6}+x-1=\dfrac{x+2}{2}\)
=>\(\dfrac{1-3x+6\left(x-1\right)}{6}=\dfrac{3\left(x+2\right)}{6}\)
=>1-3x+6x-6=3x+6
=>3x-5=3x+6
=>-5=6(vô lý)
h: \(\dfrac{3\left(2x+1\right)}{4}-5-\dfrac{3x+2}{10}=\dfrac{2\left(3x-1\right)}{5}\)
=>\(\dfrac{15\left(2x+1\right)}{20}-\dfrac{100}{20}-\dfrac{2\left(3x+2\right)}{20}=\dfrac{8\left(3x-1\right)}{20}\)
=>30x+15-100-6x-4=24x-8
=>24x-89=24x-8
=>-89=-8(vô lý)
i: \(\dfrac{2x+1}{3}-\dfrac{5x+1}{6}=\dfrac{x+1}{2}\)
=>\(\dfrac{2\left(2x+1\right)}{6}-\dfrac{5x+1}{6}=\dfrac{3x+3}{6}\)
=>4x+2-5x-1=3x+3
=>3x+3=-x+1
=>4x=-2
=>x=-1/2
j: \(\dfrac{3\left(x+3\right)}{4}+\dfrac{1}{2}=\dfrac{5x+9}{3}-\dfrac{7x-9}{4}\)
=>\(\dfrac{9\left(x+3\right)}{12}+\dfrac{6}{12}=\dfrac{4\left(5x+9\right)}{12}-\dfrac{3\left(7x-9\right)}{12}\)
=>9x+27+6=20x+36-21x+27
=>9x+33=-x+63
=>10x=30
=>x=3