Số bi xanh là: 75x\(\dfrac{40}{100}\)=30 (viên)

Số bi đỏ là: 75-30=45(viên)

        Đáp số: Bi xanh: 30 viên

                     Bi đỏ: 45 viên

(9-8)x4-2

3,5 lít dầu nặng số kg là:   

 1,3x(3,5:0,6)=1,3x\(\dfrac{35}{6}\)=\(\dfrac{91}{12}\)(kg)

                Đáp số: \(\dfrac{91}{12}\)kg

\(y-y:8=84\\ \\ \Rightarrow y-\left(y.\dfrac{1}{8}\right)=84\\ \\ \Rightarrow y.\left(1-\dfrac{1}{8}\right)=84\\ \\ y.\dfrac{7}{8}=84\\ \\ y=84:\dfrac{7}{8}=96\)

a

\(2⋮x+1\\ \\ x+1\inƯ\left(2\right)=\left\{1;2;-1;-2\right\}\\ \\ \Rightarrow x\in\left\{0;1;-2;-3\right\}\)

Vì \(x\in N\)\(\Rightarrow x\in\left\{0;1\right\}\)

Vậy \(x\in\left\{0;1\right\}\)

a

Số bị chia là: 50x10x5=2500

Đ/S: 2500

C1: \(\left(\dfrac{1}{3}+\dfrac{2}{9}\right)\)x\(\dfrac{4}{9}\)=\(\left(\dfrac{3}{9}+\dfrac{2}{9}\right)\text{x}\dfrac{4}{9}\)=\(\dfrac{5}{9}\text{x}\dfrac{4}{9}=\dfrac{20}{81}\)

C2: \(\left(\dfrac{1}{3}+\dfrac{2}{9}\right)\)x\(\dfrac{4}{9}\)=\(\dfrac{1}{3}\text{ x}\dfrac{4}{9}+\dfrac{2}{9}\text{ x}\dfrac{4}{9}\)=\(\dfrac{4}{27}+\dfrac{8}{81}=\dfrac{12}{81}+\dfrac{8}{81}=\dfrac{20}{81}\)