Question 604533
speed = distance/time
so, time = distance/speed


{{{12/x + 12/(x+2)=5}}}
{{{(12*(x+2)+12*x)/(x*(x+2))=5}}}
{{{(12x+24+12x)/(x^2+2x)=5}}}
{{{24x+24=5*(x^2+2x)}}}
{{{24x+24=5x^2+10x}}}
{{{0=5x^2+10x-24x-24}}}
{{{0=5x^2-14x-24}}}
0 = (5x + 6)*(x - 4)
5x + 6 = 0 or x - 4 = 0
5x = -6 or x = 4
5x = -6/5 or x = 4
because the speed can't be a negative number, we choose x = 4


so, x = 4