Answer:
(3)
x = 0
y = 3/7
(4)
x = 6
y = -11
Explanation:
the beginning was right, but get mistake was then to add the 2 equations but the parts with the y terms she suddenly subtracted.
no, one operation for everything. and then maybe another operation (and again for everything present).
so, some would multiply by -2 and then truly add.
or, as we will do it now to refuse as much as possible from your friend's work, we multiply by 2 and then SUBTRACT !
5x + 7y = 3
3x + 14y = 6
multiply the first equation by 2 and then subtract the second one.
10x + 14y = 6
- 3x + 14y = 6
-----------------------
7x + 0 = 0
=>
x = 0
then we use this e.g. in the first equation to get y :
5×0 + 7y = 3
7y = 3
y = 3/7
10x + 3y = 27
3x - 5y = 73
let's go e.g. for 15y (multiply the fits by 5 and the second by 3)
50x + 15y = 135
+ 9x - 15y = 219
------------------------
59x + 0. = 354
59x = 354
x = 6
10×6 + 3y = 27
60 + 3y = 27
3y = -33
y = -11