The common ratio is -5, note that each value is the previous value multiplied by -5.
Add your two totals together,
1860 + 5775 = 7635, next we multiply our answer by 1.082,
$8261.07 is the total cost.
Divide 1500 by 5 to get one fifth of the savings. Multiply that by 12 to get yearly savings. You end up with 3600.
C=x+9, c+x=99, c=99-x
So we have two equations equal to c, c=x+9 and c=99-x, since c=c:
x+9=99-x
2x+9=99
2x=90
x=45, and since c=x+9, c=54
So Charlie weighs 54 kg and his brother weighs 45 kg.
