In your mind, you could think 100% more is 200% and 50% of that is another 100% so 200% increase. Let's see on paper. x will be her current hair length.
<span>x + x + .5(x + x) </span>
<span>x + x is simply her hair length doubling. This is when it grew 100% longer. Then, from that, we have 50% more, so we have to add 50% of the x + x. </span>
<span>2x + .5x + .5x </span> <span>3x </span>
<span>Subtract our starting length. </span>
<span>3x - x = 2x </span>
<span>The difference is 2 hair lengths, or 200% her original length of hair.</span>
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