If 2x-8y=24 and 6x+7y=18, what is the value of 5x+11y

First equation can be simplified:
x − 4y = 12

Second equation:
6x + 7y = 18

Now subtract 1st equation from 2nd equation:
. (6x + 7y = 18)
− (x − 4y = 12)
-------------------
5x + 11y = 6

system of equations:
2x - 8y = 24 can be re-written as:
-6x + 24y = -72
therefore the system is:
-6x + 24y = -72
6x+7y=18
--------------
31y = 54
so y = 54/31

then solve for x

then just plug in the values for x and y into
5x + 11y

(am refraining from doing due to the uglyness of the problem)

2x-8y=24
or, x=(24+8y)/2

putting this value of x in second equation:
6[(24+8y)/2] + 7y =18
or,6(12+4y) + 7y =18
or, 72 +31y=18
or, 31y=18-72=-54
or,y=-54/31

and ,
x=(24+8y)/2
or, x = 156/31
thus 5x+11y
=5*156/31 + 11 * (-54/31)
=6

Via the substitution method

take 2x-8y=24 and solve for x
=> 2x = 24 + 8y
=> x = 12 + 4y

now substitute x = 12 + 4y into 6x+7y=18 and solve for y
=> 6(12 + 4y) + 7y = 18
=> 72 + 24y + 7y = 18
=> 31y = -54
=> y = -54/31

now substitute that result back into x = 12 + 4y
=> x = 12 + 4 * -54/31
=> x = 12 -216/31
=> x = 156/31

now substitute both x = 156/31 and y = -54/31 into 5x+11y
=> 5 * 156/31 + 11 * -54/31
=> 780/31 - 594/31
=> (780 - 594)/31
=> 186/31
=> 6

Multiply [2x-8y=24] by three, then subtract the equations.

x = 5.03226,y = -1.74194

Multiply x by 5 and y by 11, then add, and you get 6.

5x+11y=6