The first term of geometric sequence is 7 and the common ratio is -2. find the 9th term.

= 7.

Ratio means multiply/divide.
To get the next number, multiply number by common ratio.
To get a previous number, divide by common ratio.

Since we want the next number...
2nd term: 7 x -2 = -14
3rd term: -14 x -2 = 28
4th term: 28 x -2 = -56
5th term: -56 x -2 = 112

Keep going until 9th term!