Răspuns :
(a+b)-18=a-b
a-b= 1/4 *a
a-b=a/4 aducem la acelasi numitor
4a-4b=a
4a-a=4b
3a=4b
a=4b/3
(4b/3+b)-18= 4b/3 -b aducem la acelasi numitor
4b+3b-54=4b-3b
7b-54=b
7b-b=54
6b=54
b=54:6
b=9
a=4b/3= 4*9/3= 4*3=12
a-b= 1/4 *a
a-b=a/4 aducem la acelasi numitor
4a-4b=a
4a-a=4b
3a=4b
a=4b/3
(4b/3+b)-18= 4b/3 -b aducem la acelasi numitor
4b+3b-54=4b-3b
7b-54=b
7b-b=54
6b=54
b=54:6
b=9
a=4b/3= 4*9/3= 4*3=12
(x + y) = (x - y) + 18
(x - y) = x * 1/4
-------
(x + y) - (x - y) = 18
x - x + y + y = 18
2y = 18
y = 18 / 2
y = 9
x - y = x / 4
x - x / 4 = y
x(1 - 1/4) = y
3x / 4 = y
3x / 4 = 9
x = 9 * 4 / 3
x = 36 / 3
x = 12
(x - y) = x * 1/4
-------
(x + y) - (x - y) = 18
x - x + y + y = 18
2y = 18
y = 18 / 2
y = 9
x - y = x / 4
x - x / 4 = y
x(1 - 1/4) = y
3x / 4 = y
3x / 4 = 9
x = 9 * 4 / 3
x = 36 / 3
x = 12