\(\dfrac{\left(x+3\right)}{7}+\dfrac{\left(x+4\right)}{6}+\dfrac{\left(x+90\right)}{10}+3=0\\ \Leftrightarrow\dfrac{60\left(x+3\right)}{420}+\dfrac{70\left(x+4\right)}{420}+\dfrac{42\left(x+90\right)}{420}+\dfrac{1260}{420}=0\\ \Leftrightarrow60x+180+70x+280+42x+3780+1260=0\\ \Leftrightarrow172x=-5500\\ \Leftrightarrow x=-\dfrac{1375}{43}\)