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put this solution on YOUR website!Let x=# of plywood boards, y=# of lumber
"In a given day, the mill turns out twice as many units of plywood as lumber" translates to
"It makes a profit of $30 on a unit of lumber and $45 on a unit of plywood. How many of each unit must be produced and sold in order to make a profit of $12120" translates to:
So we have the following system of equations

Plug in

into the second equation. In other words, replace each

with

. Notice we've eliminated the

variables. So we now have a simple equation with one unknown.

Distribute

Combine like terms on the left side

Divide both sides by 120 to isolate y

Divide
Now that we know that

, we can plug this into

to find

Substitute

for each

Simplify
So our answer is

and

which also looks like
This means that they must sell 202 units of plywood and 101 units of lumber to obtain a profit of $12,120