a) \(\dfrac{1}{5}\)+\(\dfrac{4}{5}\):x=\(\dfrac{3}{4}\)

\(\dfrac{4}{5}\):x=\(\dfrac{3}{4}\)-\(\dfrac{1}{5}\)

\(\dfrac{4}{5}\):x=\(\dfrac{11}{20}\)

x=\(\dfrac{4}{5}\):\(\dfrac{11}{20}\)

x=\(\dfrac{16}{11}\)

b) x+\(\dfrac{1}{2}\)=1-x

2x=1-\(\dfrac{1}{2}\)

2x=\(\dfrac{1}{2}\)

x=\(\dfrac{1}{2}\):2

x=\(\dfrac{1}{4}\)
 15+45:x=0

a) \(\dfrac{2}{3}\).\(\dfrac{5}{4}\)-\(\dfrac{3}{4}\).\(\dfrac{2}{3}\)=\(\dfrac{2}{3}\).(\(\dfrac{5}{4}\)-\(\dfrac{3}{4}\))=\(\dfrac{2}{3}\).\(\dfrac{1}{2}\)=\(\dfrac{1}{3}\)
b)2.(\(\dfrac{-3}{2}\))\(^2\)-\(\dfrac{7}{2}\)=2.\(\dfrac{9}{4}\)-\(\dfrac{7}{2}\)=\(\dfrac{9}{2}\)-\(\dfrac{7}{2}\)=1

c)-\(\dfrac{3}{4}\).\(5\dfrac{3}{13}\)-0,75.\(\dfrac{36}{13}\)=-\(\dfrac{3}{4}\).\(5\dfrac{3}{13}\)-\(\dfrac{3}{4}\).\(\dfrac{36}{13}\)=-\(\dfrac{3}{4}\).(\(5\dfrac{3}{13}\)+\(\dfrac{36}{13}\))=-\(\dfrac{3}{4}\).8=-6