Question

21/x=48/96. 70/b=20/80. 50/20=x/72

Answer 1

`\begin{gathered} (21)/(x)=(48)/(96) \\ \text{Cross multiplying both sides of the equation,} \\ 21(96)\text{ = 48(x)} \\ x=(21(96))/(48)=21(2)=42 \\ x=42\text{.} \\ \\ (70)/(b)=(20)/(80) \\ \text{Cross multiplying,} \\ 70(80)=20(b) \\ \text{Dividing both sides by 20.} \\ (70(80))/(20)=(20b)/(20) \\ b=70(4)=280 \\ b=280 \\ \\ (50)/(20)=(x)/(72) \\ \text{Cross multiplying,} \\ 50(72)=x(20) \\ \text{Dividing both sides of the equation by 20,} \\ (50(720)/(20)=(x(20))/(20) \\ x=50(36)=1800 \\ x=1800 \end{gathered}`

In summary, the respective values of the unknown variables in the equations are 42, 280, and 1800.