If $a: b: c = 3: 4: 7,$ then the ratio $(a+b+c): c$ is equal to

The ratio between the present ages of $P$ and $Q$ is $5:7$ respectively. If the difference between $Q$'s present age and $P$'s age after $6$ years is $2$,what is the total of $P$'s and $Q$'s present ages (in years)?

Present ages of $X$ and $Y$ are in the ratio $5: 6$ respectively. Seven years hence,this ratio will become $6: 7$ respectively. What is $X$'s present age in years?

Gold is $19$ times as heavy as water and copper is $9$ times as heavy as water. In what ratio should these be mixed to get an alloy $15$ times as heavy as water?

If $A : B : C = 2 : 3 : 4,$ then $\frac{A}{B} : \frac{B}{C} : \frac{C}{A}$ is equal to

Find the sub-duplicate ratio of $81: 64$.