Question 106344
1. y=2x+7
   y=5x+4
{{{2x+7=5x+4}}}
{{{2x-5x=4-7}}}
{{{-3x=-3}}}
{{{x=1}}}
------------------
{{{y=2(1)+7}}}
{{{y=2+7}}}
{{{y=9}}}
====================
2. 3x-2y=0
   x+y=-5
{{{x=-5-y}}}
{{{3(-5-y)-2y=0}}}
{{{-15-3y-2y=0}}}
{{{-5y-15=0}}}
{{{-5y=15}}}
{{{y=-3}}}
------------------
{{{x+(-3)=-5}}}
{{{x=-5+3}}}
{{{x=-2}}}
=========================
3. 4x+3y=-3 
   2x+y=-1
{{{y=-1-2x}}}
{{{4x+3(-1-2x)=-3}}}
{{{4x-3-6x=-3}}}
{{{-2x-3=-3}}}
{{{-2x=0}}}
{{{x=0}}}
-------------------
{{{4(0)+3y=-3}}}
{{{3y=-3}}}
{{{y=-1}}}
===========================
4. 2x-4y= 3.8 
   3x-y=17.7
{{{y=3x-17.7}}}
2x-4(3x-17.7)=3.8}}}
{{{2x-12x+70.8=3.8}}}
{{{-10x=-67}}}
{{{x=6.7}}}
--------------------
{{{2(6.7)-4y=3.8}}}
{{{13.4-4y=3.8}}}
{{{-4y=-9.6}}}
{{{y=2.4}}}
:)