ANSWER
400%
EXPLANATION
The percent of increase between two values is:
[tex]\frac{\text{ final value - starting value}}{\text{ starting value}}\times100[/tex]In this problem the final value is 300 and the starting value is 60:
[tex]\frac{300-60}{60}\times100=\frac{240}{60}\times100=4\times100=400\text{ \%}[/tex]