The ratio of present ages of Suresh and Manish are 5 : 1 respectively. After how many years the ratio of the ages of Suresh and Manish will become 3 : 1 if the present age of Manish is 7 years -

In the following question, by using which mathematical operators will the expression become correct?
30 ? 6 ? 4 ? 5 ? 4

Which two numbers should be interchanged to make the following equation correct?
7 – 8 ÷ 4 + 5 × 3 = 8 × 3 + 6 ÷ 2 – 3

There were 15 persons in a group, they shook hands with each other, then tell how many times the total number of hands were shaken -

Which two signs should be interchanged to make two given equation correct.
4 × 8 ÷ 16 – 4 + 6 – 3 + 2 = 32

If -4$1 = 4, 7$-7 = 49 and 3$1 = -3, then find the value of -8$-5 = ?

Damini is twice as old as Hari. Hari is 5 years older than Nipa. In 5 years, Damini will be three times as old as Nipa. How old is Hari now?

The average age of father and his son is 22 years. The ratio of their ages is 10 : 1 respectively. What is the age of the son?