Find the missing number in the following series:

4? 17 51 56 168 i know the answer is 12 (someone else said) but i don't know why. Can anyone explain the pattern?

A certain sum amounts to 9440 in 3 years and 10400 in 5 years. Find the sum and the rate per cent.

Divide 3/5 by its reciprocal

Rachelle can walk 2.5 miles in 40 minutes. At this rate, how far can she walk in 1 hour?

Simplify 5 (x - 1) - 5

Parallel to y - 3 = - (x + 1) and passes through (4, 2). Trish states that the parallel line is y - 2 = - 1 (x - 4). Demetri states that the parallel line is y = - x + 6. Are the students correct? Explain.

A newspaper reporter wants to know how popular the hobby of bird watching is in the city. He asked people at the local bird refuge if they watched birds as a hobby. Which of the following best explains whether the reporters data is valid or not?

I am very confused on how to figure out if y = 3/4x is proportional?

Alison wants to buy a mountain bike for $339.12. If she saves $28.26 each month, in how many months will she be able to buy the bike?

At 12 o'clock the temperature was 7°C. The temperature decreased by - 20°C. What is the new temperature?

Ashleys rentals charges $27.50 per hour to rent a surfboard and a wetsuit. Darlas surf shop charges $23.25 per hour to rent a surfboard plus $17 extra for a wetsuit.