Event A : The marble selected has an even number. Event B : The marble selected has a number from 3 to 6 .

Six-sided polygon that includes two isosceles right triangles, one with height and base of 25 feet,
triangle1 area= height * base /2
triangle1 area= 25* 25/2= 312.5

the other height and base of 8 feet,
triangle2 area= height * base /2
triangle2 area= 8* 8/2= 32

and one rectangle measuring 35 feet by 8 feet
rectangle area= height * base 
rectangle area= 35* 8= 280

Total area= triangle1 area + triangle2 area + rectangle area= 312.5+ 32+280= 624.5