Answer
The percent change is 50%
Work Step by Step
Step 1) 18-12=6 ... The student starts out with 12. The question is asking: If he were to have 18 what percent of 12 would be added to achieve this goal? Subtract 12 from 18.
Step 2) 6/12=0.5 (6 divided by 12) ... With the number increased known of 6 we now must understand what else is being asked. What is the percent change? In other words, "What percent of 12 is 6?" or "How much of 12 is 6 in terms of percentage?". In order to find this out, you divide 6 by 12. NOT the other way around. (Lots of people make that mistake) This will give you 0.5 a decimal.
Step 3) 0.54'100=50% (0.5 multiplied by 100) ... The question is asking for a percent and the answer we received was in decimal form. In order to change the decimal into a percentage. simply multiply the decimal by 100. Your final answer should be 50%