Question 193889
{{{ A(x) = x^2+5x+6}}} 

a) Find A(5). 
{{{ A(x) = x^2+5x+6}}} 
{{{ A(5) = 5^2+5*5+6}}} 
{{{ A(5) = 25+25+6}}} 
{{{ A(5) = 56}}} 

b) If the height of the sail is x +3 meters, then what is the length of the base of the sail?
Area of a triangle is {{{A = bh/2}}}
{{{x^2+5x+6 = b *(x+3)/2}}}
{{{2x^2 + 10x + 12 = b * (x+3)}}}
{{{(2x^2 + 10x + 12)/(x+3) = b}}}
{{{((x+3)(2x + 4))/(x+3) = b}}}
{{{2x+4 = b }}}

If you need a nice place to factor expressions. try this 
http://72.3.253.76/webMathematica3/quickmath/page.jsp?s1=algebra&s2=factor&s3=basic