1) the x-coordinate of the system can be given as follow:
2x+3y = 5 (i)
3x+5y =7 (ii)
we multiply (i) by 5 and (ii) by 3, we have
10x+15y = 25 (a)
9x+15y =21 (b)
so (a) - (b) implies x = 4,
2) We do the same method for
{2x + y = 2
{3x + 4y = -22,
and we found y = -10,
3) for the last one,
{5x + 4y = 2
{-2y = 8 + 4x
this system is equivalent to
{5x + 4y = 2 (i)
{4x + 2y = - 8 (ii)
so, multiply (i) by 4 and (ii) by 5, and we have
20x + 16y = 8 (a)
20x + 10y = -40 (b)
elimination of x gives 6y = 48 then y= 8, we can find x fastly by replacing y=8 in (i), so 5x +4(8) =2, which implies x= -6
finally the solution is S= {(-6, 8)}
