hi
7x+2y = -5
3x-y = 9
first thing is to define one letter by it's value in the second.
here we have 3x-y = 9 so
-y = 9 -3x
y = 3x-9
then with y = 3x-9 ,
7x +2y = -5 ⇔ 7x + 2 ( 3x-9) = -5
so :
7x + 2 ( 3x-9) = -5
7x +6x -18 = -5
13x -18 = -5
13x = -5 +18
13x = 13
x = 13/13
x = 1
as : y = 3x-9 so bhy remplacing X by it's value
y = 3 (1) - 9 = 3-9 = -6
y = -6
solutions are :
x = 1 and y = -6
let' s check to be sure :
7 (1) + 2 (-6) = 7 -12 = -5
and 3(1) - (-6) = 3 +6 = 9
