Solve this system by using either substitution or elimination.?

try to make the coefficient of x or y the same, so u can eliminate one variable

i'll do x
3x-6y=7.5 (i multiplied the whole equation by 1.5)
-3x+6y=-12

add them up
0+0=-4.5

there is no solution.

2x - 4y = 5 (solve by using elimination)
-3x + 6y = -12

2x - 4y = 5
3(2x - 4y) = 3(5)
6x - 12y = 15

-3x + 6y = -12
2(-3x + 6y) = 2(-12)
-6x + 12y = -24

...6x - 12y = 15
+) -6x + 12y = -24 (addition)
-----------------------------------
0 = -9
(no solutions)

Cannot be done.

on using eliminationa method,

we end up with
0=9
this is an impossible statement.
so the pair of equations has no solutions.
If u want plot the equations on a graph and see for ur self that the lines dont intersect each other.

for further clarification just mail to me :)

3(2x - 4y = 5)----------->6x - 12y = 15
2(-3x + 6y = -12)------>-6x + 12y = -24

These lines are parallel and have no points in common.