Which two signs should be interchanged to make the following equation correct?
20 ÷ 20 + 20 – 25 × 25=419

A man is 3 years older than his wife and four times as old as his son. If the son becomes 15 years old after 3 years, what is the present age of the wife? 

Identify the symbols to be inserted to make the expression correct.
24 Δ 4 Δ 5 Δ 4

Select the correct set of symbols:
34  16  4  12  = 26

If P means -, Q means +, R means x and  S means ÷ then what is the value of  8 R6S3Q5P9 

If 16 Δ 4= 64 and 216 @ 8=27 and what is the value of 8 Δ 5@ 4 =?

If ‘+’ means ‘-‘; ‘-‘ means ‘×’; ‘×’ means ‘÷’ and ‘÷’ means ‘+’, then
25×5÷30+8 – 2 =?

There are deer and peacocks in a zoo. By counting heads they are 80. And the number of their legs is 200. How many peacocks are there?