6a=b
Explanation
Looking at the non fraction numbers the first set is 0,0 which provides no information. Looking at the second 3,18 shows us that b is greater than a, so a must be added or multiplied by something adding would get us +15 multiplying would get us x6. Looking at the first set again adding would get b to 15 while multiplying would keep us at zero. Since multiplying is the rule that shows the proper output. Checking with the rest of the table using the rule 6a=b can determine if the equation is correct or not.