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>
Y= 18 gallons-2(h) y is what you're trying to find out and since there are 18 gallons in the tank after every hour you would have 2 less gallons. So, you can multiply how many hours he's been driving by the 2 gallons and subtract it from 18
