A ) it is asking you to do the average of 3 months, so you add up the first 3 and divide by 3 (5760+5820+5760)/3 = 5780 then you do the next 3 months (including feb to apr) and divided by 3 again and same for the rest.
B ) It is normal definition of Seasonal Variations which is it is actuals - trend The usual increases in November and December are seasonal variations (they are recurring every year for christmasy in this instance)
C ) it is indexes, you have January figure Actual x RTI for January (which it is the base) / RTI the month which are you are calculating
129000 X 170 / 170 for January 132000 x 170 / 172 for Feb 135000 x 170 / 174 for March
D ) y=a+bx is the high low method
x = units
200 units £5000 2000 units £14000
14000-5000 = 9000 2000 - 200 = 1800 9000/1800 = £5 which is b
£5 x 200 = £1000 => £5000 - £1000 => £4000 is the fixed figure
hence a is £4000, b is £5 and x is the units number
Comments
B ) It is normal definition of Seasonal Variations which is it is actuals - trend
The usual increases in November and December are seasonal variations (they are recurring every year for christmasy in this instance)
C ) it is indexes, you have January figure Actual x RTI for January (which it is the base) / RTI the month which are you are calculating
129000 X 170 / 170 for January
132000 x 170 / 172 for Feb
135000 x 170 / 174 for March
D ) y=a+bx is the high low method
x = units
200 units £5000
2000 units £14000
14000-5000 = 9000
2000 - 200 = 1800
9000/1800 = £5 which is b
£5 x 200 = £1000 => £5000 - £1000 => £4000 is the fixed figure
hence a is £4000, b is £5 and x is the units number
Hope this helps.