Răspuns :
x+y = 23 ⇒x =23-y
3x + 7y = 113
3 (23-y) + 7y = 113
69 - 3y +7y = 113
69 +4y = 113
4y = 113-69
4y = 44
y = 11
x = 23 - 11
x= 12
3x + 7y = 113
3 (23-y) + 7y = 113
69 - 3y +7y = 113
69 +4y = 113
4y = 113-69
4y = 44
y = 11
x = 23 - 11
x= 12
x+y=23(inmultim cu 3)
3x+3y=69
3x+7y=113
7y-3y=113-69
4y=44
y=44:4
y=11
x+11=23
x=23-11
x=12
3x+3y=69
3x+7y=113
7y-3y=113-69
4y=44
y=44:4
y=11
x+11=23
x=23-11
x=12