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

The following equation is incorrect. Which two signs should be interchanged to correct the equation?
12 + 10 - 28 ÷ 7 x 4 = 48

Mani is double the age of Prabhu , Ramona is half the age of Prabhu . If Mani is sixty years old , find out the age a Ramona . 

John ' s age is 42 years and Kelvin ' s age is 26 years and how many years ago was Kelvin ' s age half of John ' s age ? 

Out of 100 families in the neighbourhood, 50 members have radios , 75 members have TVs and 25 members have VCRs . Only 10 families have all three and each VCR owner also has a TV . If some families have radio only , how many have only TV ? 

In the following question, correct the equation by interchanging two numbers.
9 × 3 – 8 ÷ 2 + 7 = 26

If “P” denotes “divided by”, “R” denotes “added to”, “S” denotes “subtracted from” and “Q” denotes “multiplied by”, then
48 P 4 R 3 Q 4 S 6 Q 4 = ?

In a school, the bell is rung once after each half an hour. The school starts at 8:00 a.m. and closes at 1: 30 p.m. The bell is rung 3 times continuously, at the time of beginning, at the time of lunch break at 10:00 and 10:30 a.m. and at the end. How many times is the bell rung every day?