Ineed solving a system of linear equation, and it says to solve it by substitution.
how would i do it?
2x - 3y = -24
x + 6y = 18

2x - 3y = -24
x+ 6y = 18

you solve the first one by the x:

2x = -24 + 3y

x = (-24+3y)/2

then you substitute what you found in the other equation and you solve by y

(-24+3y)/2 + 6y = 18                   multiply everything by 2

-24 + 3y + 12y = 36

3y + 12y = 36 + 24

15y = 60

y = 60/15

y = 4

Good job! You found your y! :D

Now let's substitute the y in the first equation with 4:

2x - 3(4) = -24

2x - 12 = -24

2x = -24 + 12

2x = -12

x = -12/2

x= -6

Done!! ;) 

First solve for x in the second equation (x=-6y+18).then substitute -6y+18 in the first equation and solve for y.after solving for y then substitute it in one of the equation and then solve for x.
2x-3y=-25
x+6y=18

x=-6y+18
2(-6y+18)-3y=-24
-12y+36-3y=-24
-15y+36=-24
-15y=-24-36
-15y=-60
y=4

x+6(4)=18
x+24=18
x=18-24
x=-6

y=4,x=-6

Set square i think so