If $0.75 : x :: 5 : 8,$ then $x$ is equal to

The difference between the ages of Meena and Seema is $3 \ yr$ and the ratio between their ages is $7: 8$. What is the sum of their ages (in $yr$)?

$P$ varies inversely with the product of $Q$ and $R$. When $Q = 6$ and $R = 12$,$P = 75$. When $Q = 5$ and $R = 10$,what is the value of $P$?

$A$ person's present age is two-fifth of the age of his mother. After $8$ years,he will be one-half of the age of his mother. How old is the mother at present (in $years$)?

Two numbers are in the ratio $3: 5$. If each number is increased by $10$,the ratio becomes $5: 7$. The numbers are:

If the annual income of $A$,$B$,and $C$ is in the ratio $1:3:7$ and the total annual income of $A$ and $C$ is $Rs. 800,000$,then the monthly salary of $B$ (in $Rs.$) is: (in $,000$)