a) \(x-\dfrac{-1}{3}=2\dfrac{1}{4}\)
\(x+\dfrac{1}{3}=\dfrac{9}{4}\)
\(x=\dfrac{9}{4}-\dfrac{1}{3}\)
\(x=\dfrac{23}{12}\)
b) \(\dfrac{1}{3}+\dfrac{2}{3}\div x=\dfrac{\left(-4\right)}{5}\)
\(\dfrac{1}{3}+\dfrac{2}{3}\div\dfrac{1}{x}=-\dfrac{4}{5}\)
\(\dfrac{1}{3}+\dfrac{2x}{3}=-\dfrac{4}{5}\)
\(\dfrac{5}{15}+\dfrac{10x}{15}=-\dfrac{12}{15}\)
\(17x+10=0\)
\(17x=-10\)
\(x=\left(-10\right)\div17\)
\(x=-\dfrac{10}{17}\)
c) \(x\div\dfrac{\left(-2\right)}{5}-\dfrac{3}{7}=\left(\dfrac{-1}{3}\right)\)
\(x\div\dfrac{\left(-2\right)}{5}=\dfrac{-1}{3}+\dfrac{3}{7}\)
\(x\div-\dfrac{2}{5}=\dfrac{2}{21}\)
\(x=\dfrac{2}{21}\times\dfrac{-2}{5}\)
\(x=-\dfrac{4}{105}\)
