Zarrolou

2^(2(x+y))=2^(3(10)) --same basis--> 2(x+y)=3*10 we have to see if this relation is true 1) x - y = 9 by itself is not sufficient: x=10 y=1 10 - 1 =9 OK ; but 2(10+1) does not equal 30 but x=12 y=3 12 - 3= 9 OK ; 2(12 + 3) = 30 OK 2) y/x=1/4 is not sufficient: x=4 y =1 1/4 = 1/4 OK; but 2(4+1) does not equal 30 but x=12 y=3 3/12= 1/4 OK; 2(12+3) = 30 OK 3) only combining x - y = 9 with y/x = 1/4 we can find the solution ( which is x=12 y=3) hope this helps

D or E. I pick D...