Question 155455
{{{3x+5y=25}}}
{{{-7x+4y=20}}}

using elimination method 
and doing:
1st eq by (4) and 2nd by(-5) 

{{{12x+20y=100}}}
{{{35x-20y=-100}}}
adding:
{{{47x=0}}}
then {{{x=0}}}

using 1st eq
{{{5y=25}}}
then
{{{y=5}}}


Answer: x=0,y=5