Question

a) 3×+y=20 2×-y=30 b) -×+4×=30 ×-2y=10 c)-2×+3y=50 2×-y=60

Answer 1

a)

3x+y=20

2x-y=30

5x=50

x=50/5=10

3x+y=20

3×10+y=20

30+y=20

y=-10

b)

-x+4x=30

x-2y=10

-x+4x=30

3x=30

x=30/3=10

x-2y=10

10-2y=10

-2y=-10+10 ×(-1)

2y=+10-10

2y=0

y=0/2=0

c)

-2x+3y=50

2x-y=60

2y=110

y=110/2=55

2x-y=60

2x-55=60

2x=60+55

2x=115

x=115/2

Answer 2

a)

3×+y=20

2×-y=30

5x = 50

x = 10

30 + y = 20

y = -10

S = (10, -10)

b)

-×+4y =30

×-2y=10

2y = 40

y = 20

-x + 80 = 30

x = 50

S = (50, 20)

c)

-2×+3y=50

2×-y=60

2y = 110

y = 55

2x = 60 + 55

x = 115/2