-4d + 2e + f = -20
pleasee help meeeee
There is nothing you can do with this. When you have more than
one unknown (one variable), you need more than one equation.
You manipulate the equations by multiplying them so two of them
have the same co-efficient for one of the variables. Then, you add
or subtract those equations to eliminate the variable. Keep doing that
until you have one equation with only one variable. Solve that equation
and plug the value into one of the equations to solve for another
variable. Keep adding and subtracting equations to isolate one
of the variables, solve for it, and use that to help solve another equation.
One equation with two or more variables is a lost cause.