WBCS Mains 2018 Official Paper-VI

The age of a father is twice that of his elder son. Ten years hence, the age of the father will be three times that of his younger son. If the difference between the ages of the two sons is $15\text{years}$, the current age of the father is:

Find the missing character in the following circular/triangular pattern sequence. Going clockwise, the numbers are:

In a group of persons travelling in a bus, $6$ persons can speak French, $15$ can speak Spanish and $6$ can speak English. In that group, none can speak any other language. If $2$ persons in the group can speak two languages and one person can speak all the three languages, then how many persons are there in the group?

If $A+B>C+D$ and $B+C>A+D$, then it is definite that