Step-by-step explanation:
x +2y = 9. .....(1)
x - 2y = 5. .....(2)
from eqn (1)
x + 2y = 9
x = 9 - 2y.
substitute x = 9 - 2y into eqn (2)
9 - 2y - 2y = 5
-4y = 5 - 9
-4y = -4
y = 1
sub y = 1 into eqn (1)
x + 2y = 9
x + 2(1) = 9
x + 2 = 9
x = 9 - 2
x = 7.
(2) x + y = 9 ....(1)
x - 2y = 0 .....(2)
from eqn (2)
x - 2y = 0
x =0 + 2y
substitute x = 2y into eqn (1)
x + y = 9
(2y) + y = 9
3y = 9
y = 3
substitute y = 3 into eqn (2)
x - 2y = 0
x - 2(3) = 0
x - 6 = 0
x = 6.
(3) 2x + 7y = 5. ....(1)
2x + 3y = 9. .....(2)
from eqn (1)
2x + 7y = 5
7y = 5 - 2x
y = (5 - 2x)/7
sub y = (5 - 2x)/7 into eqn (2)
2x + 3y = 9
2x + 3(5 - 2x)/7 = 9
2x + (15 - 6x)/7 = 9
multiply through by 7
14x + 15 - 6x = 63
14x - 6x = 63 - 15
8x = 48
x = 6
sub x = 6 into eqn (1)
2x + 7y = 5
2(6) + 7y = 5
12 + 7y = 5
7y = 5 - 12
7y = -7
y = -1
