Answer: The number of calories increased by 20%.
Step-by-step explanation:
Given : The doctor recommended that Mike increase the number of calories he burns working out from 1,500 to 1,800.
Previous number of calories he used to burn = 1,500
Increase in calories = 1800-1500=300
Now , the percent increase in calories = 

Hence , the number of calories increased by 20%.
4x = -36 Subtract 10 from both sides
x = -9 Divide by 4 on both sides
0.24/.012 Answer= 20
You just divide the .24 by .012