Help!! nth term maths homework

[MrsFogi]

Hi can someone help me to retain the facade of being "good" at maths? DD's question is:
Find the nth term of this number sequence
15, 12, 9, 6...
Can someone tell me how to do it? I have absolutely no idea (I can see it decreases by 3 each time but don't know how that relates to this nth term business).
Thanks!

Been a while since I've done this so
1st term = 15
2nd term = 12
3rd term = 9
4th term = 6

n is used to replace any number term.

The nth term will relate to the gap between the numbers so start with 3n.

The numbers get smaller so it will be a minus number so -3n

replace n with 1 and try to work out how to get to 15
-3×1 = -3, add 18 to get to 15

see if that works for number 2
-3×2 = -6, add 18 gives you 12 so is correct

try with 3 to make sure
-3×3 = -9, add 18 gives you 9

so the pattern is -3 x the number, take away add 18.

Which makes the answer -3n+18

not take away add 18!!
just add 18.
Rubbish at multitasking.