SAT Question 040f2a84: Percentages answer and explanation with Desmos solution

8. It’s given that the regular price of a shirt at a store is \11.70$,andthesalepriceoftheshirtis＄80\%$ less than the regular price. It follows that the sale price of the shirt is $11.70 \left( 1 - \frac{80}{100} \right), or \11.70 \left( 1 - 0.8 \right), which is equivalent to \2.34$.It’salsogiventhatthesalepriceoftheshirtis＄30\%$ greater than the store’s cost for the shirt. Let $x$ represent the store’s cost for the shirt. It follows that ＄2.34 = \left( 1 + \frac{30}{100} \right) x$,or＄2.34=1.3x$. Dividing both sides of this equation by ＄1.3$yields$x = 1.80$.Therefore,thestore’scost,indollars,fortheshirtis＄1.80$. Note that 9/5, 1.8, and 1.80 are examples of ways to enter a correct answer.