Okay. To solve this problem, all we have to do is find the amount of change by subtraction. 50 - 30 = 20. You find the percent of change by writing out a proportion. Do change/original = x/100. You set it up like this to find the percentage. With the numbers plugged in, it’s 20/30 = x/100. Cross multiply in order to get 2,000 = 30x. Now, divide each side by 30 to isolate the “x”. 2,000/ 30 is 66.6666 and the 6ms repeating or 67 when rounded to the nearest whole number. The percent markup is approx. 67%.