Evaluate s7 for 5+10+20+40+ (only the sum)

Anne is twice as old as bill, and bill is 3 years older than christie. the sum of anne s and christie s ages equal 72. find their age difference.?

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

Parabolas y=−2x^2 and y=2x^2 +k intersect at points a and b that are in the third and the fourth quadrants respectively. find k if length of the segment ab is 5.