$\displaystyle \displaystyle y=- \frac {4x}{3}+12.33 $

$\displaystyle \displaystyle y= \frac {3x}{4}+4 $

so let's say from second you express the x like :

$\displaystyle \displaystyle y= \frac {3x}{4}+4 \Rightarrow 4y=3x+16 \Rightarrow 3x=4y-16 \Rightarrow x= \frac {4y-16}{3} $

and put in first one ....

$\displaystyle \displaystyle y=- \frac {4x}{3}+12.33 $

$\displaystyle \displaystyle y=- \frac {4(\frac {4y-16}{3} )}{3}+12.33 $

$\displaystyle \displaystyle y=- \frac {\frac {16y-64}{3} }{3} +12.33 $

so you solve for y.... and just get it back in to equation for x

$\displaystyle \displaystyle x = \frac {4y-16}{3} $

and you should get that for x=4 they intersect