Question

A) X + 2Y = 20
    2X + Y = 25
B) 2X - Y = 0
    X + Y = 15

Answer 1

a) x= 20-2y
2×(20-2y)+y= 25
40-4y+y= 25
-3y= 25-40
-3y= -15 . (-1)
y= 15/3
y= 5.

x= 20-2y
x= 20-2×5
x= 20-10
x= 10.

b) corta o -y e o y.
2x+x= 15
3x= 15
x= 15/3
x= 5.

x+y= 15
5+y= 15
y= 15-5
y= 10