A particle moving in straight line with constant acceleration of 4m/s^2 has initial velocity of 11m/s

How far does it travel in 2nd second of its motion?

How far does it travel in 8th second of its motion?

An object moving with a velocity of 42m/s is stopped in 7 seconds.

How far has it travelled?

Isn't that 42+36+30+24+18+12+6 = 168? But answer is 147.