Question

A) {2x-3y=10
{2x-4y=12

B){x+y=16
{2x+y=20

D){-2x+3y=16
{2x+y=18

F){3x+y=16
{x-y=8

G){x+y=6
{2+y=9

Answer 1

A)

2x-3y=10
2x-4y=12 (×-1)

2x-3y=10
-2x+4y=-12 (+)
---------------
y = -2

2x-3×(-2)=10
2x+6=10
x=(10-6)÷2=4÷2
x = 2

B)

x+y=16 | y = 16-x
2x+y=20
2x+16-x=20
x=20-16
x = 4

y=16-4
y = 12

D)

-2x+3y=16
2x+y=18 (+)
----------------
4y = 34
y = 34/4
y = 8,5

2x+8,5=18
2x=18-8,5
x=9,5÷2
x = 4,75

F)

3x+y=16
x-y=8 (+)
-------------
4x = 24
x = 24÷4
x = 6

6-y=8
6-8=y
y = -2

G)

x+y=6
2+y=9
y = 9-2
y = 7

x+7=6
x=6-7
x = -1