Which formula can be used to find the nth term of the sequence 0.8, 0.72, 0.648

Can someone me my sister? she is in third grade. 50 points and brainlist! ones that are not answered. plz and thx!

Sole with work in 10 years, the average number of hours of tv watched per week by teenagers dropped from 23.9 to 21.4. find the percent of change.

Gabriel determined that his total cost would be represented by 2.5x + 2y – 2. his sister states that the expression should be x + x + 0.5x + y + y – 2. who is correct? explain.