When using substitution, we are imputing an equation in place of a variable to eliminate one of the variables in the equation so that we can solve for the remaining variable.
For this example, we will be plugging in (-4y+12) wherever "x" is in the other equation.
3/4 x -5y = 7
3/4(-4y+12) -5y =7
((3/4)(-4y))+((3/4)12)-5y=7
-3y+9-5y=7
-8y= -2
y=(1/4)
Now find "x" by plugging in the y-value.
x=(-4*(1/4))+12
x= -1 +12
x=11
any questions? feel free to comment below!