To find the actual discount, multiply the discount rate by the original amount 'x'. To find the sale price, subtract the actual discount from the original amount 'x' and equate this to given sale price.
Standard form is ax + by = c. Begin our transformation by multiplying both sides by 2 to get rid of the fraction. Notice that ax + by = c does not allow for fractions. Doing that multiplication gives us 2y=-x + 3. Now move the x over by the y by addition. x + 2y = 3. And there you go!