What is the sum of the first ten terms in the geometric series 4 – 12 + 36 – 108 +

This is a geometric 
first term is a = 4

2nd term is mult by 3 to give us 4( 31)

3rd term is 4( 32)

4rth term is 4( 33)

and the 12th term is 4( 311)

so a is 4 and the common ratio (r) is equal to 3
that's all you need to know.

The formula for the sum of the 12 terms in geometric is:
S(n)=a(1−rn1−r)

substituting a=4 and r=3, we get: 
s(12)=4(1−3121−3) or a total sum of 1,062,880.

you can confirm this formula is true by calculating the sum of the first 4 terms and comparing s(4)=4(1−341−3)

All you have to do is figure out what the first term is and then figure out the common ratio between them!

Where is the problem

The percent discount was 120