Question 8318
sister=x
cousin=26+x


product:  multiply the two 
(x)(26+x)=560
{{{26x+x^2}}}=560
{{{x^2+26x-560}}}=0
(x+40)(x-14)=0


if x+40=0, x=-40  <--since her sister can't be a negative age, we know it must use (x-14)=0


if x-14=0, x=14


Your sister is 14 years old