Let us assume that the total area of the wall to be painted is w.
Then Jason painted an area of (1/4)w on Monday
And he painted (2)(1/4)w on Tuesday
So to find the unpainted area, we just take the whole wall area to be painted (which is w) and subtract out the amounts painted on Monday and Tuesday, which are shown above.
So the unpainted area (U) would be shown by the following expression:
U = w - (1/4)w - (2)(1/4)w
We can simplify this expression by factoring out w
U = w(1 - 1/4 - 1/2)
U = w (1/4) or w/4
So all Jason needs to do is paint as much of the wall as he did on Monday, and he will be done!
You want to make either the length or width variable (I chose the width variable to be by itself. It doesn't matter) by itself by:
Divide both sides by 2. (p) ÷ 2 = (2w + 2l) ÷ 2
Subtract both sides by either length or width depending on what variable you chose to make by itself (in this case I subtracted the length variable because I wanted the width variable by itself). p/2 - l = w
You replace w with the equation above p/2 - l = w
Multiply out the L.
Plug in all your numbers a = 110 and p = 42
Move everything to the left side so would be positive (makes the equation easier when is positive).
Factor.
Make each parenthesis set equal to 0.
Add.
By doing this you solve for both the width and length so the answer is: w = 11 L = 10