Let $x$ be the original price. Express the sale price, $34$, as a percentage (in decimal form) of $x$.

Once you have an equation like $0.85x = 34$, isolate $x$ by dividing both sides by the coefficient of $x$.

In Desmos, type 34/0.85 into an expression line. The numeric output shown by Desmos is the original price of the sweater before the 15% discount.

A 15% discount means the customer pays the remaining 100% − 15% = 85% of the original price.

In decimal form, 85% is $0.85$. So:

• Sale price = $0.85 \times$ (original price).

Let $x$ be the original price of the sweater in dollars.

The sale price is given as $34$, and this equals 85% of the original price:

To solve for $x$, divide both sides of the equation by $0.85$:

You can think of $0.85$ as $\frac{85}{100} = \frac{17}{20}$, so:

Since $34 = 2 \cdot 17$:

So the original price of the sweater was 40 dollars.