Solution :
Transforming given equations :

From above equations we can see that equation 1) has largest percentage growth rate and the percent growth rate is 12% .
Hence, this is the required solution.
Answer:
He must earn $2,400 to cover both leisure and $2,160 for school expenses.
Step-by-step explanation:
Let the total amount Ken must earn be k. Then 10% of that would cover leisure activities and the remaining 90% specifically for school expenses.
Then 0.90k = $2,160, and k = $2,400.
He must earn $2,400 to cover both leisure and $2,160 for school expenses.