Question 470226
Let {{{x}}} is Peter's age
Then his brother is {{{x-3}}} years old.
The product of their ages is {{{x(x-3)=270}}}
{{{x^2-3x-270=0}}}
 {{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 
 {{{x = (-(-3) +- sqrt( (-3)^2-4*1*(-270) ))/(2*1) }}} 
 {{{x = (3 +- sqrt( 1089 ))/2 }}} 
{{{x1=(3-33)/2=-15<0}}} extraneous root
{{{x2=(3+33)/2=36/2=18}}} is Peter's age
Answer: Peter is 18 years old