Question 164969
solve similtaneously: multiply top equation by -3 then add to 2nd equation 

-3({{{ sqrt(x)-2sqrt(y)=-1}}}) you get {{{-3sqrt(x)+6sqrt(y)= 3}}} 
                                add to {{{ 3sqrt(x)+4sqrt(y)=17}}} and the x terms cancel out so you end up with {{{10sqrt(y)=20}}}. now square both sides and you get 100y=400  y=4 plugin y=4 to either equation, I chose the 1st, to get find x.    sqrt(x)-2sqrt(4)=-1 so sqrt(x)-2(2)=-1  and sqrt(x)=3  now square both terms to get rid of sqrt(x) and your left with x=9  

answer: x=9
        y=4