Solve plzzzz

frndz.. i am totally unaware how to solve these prblms.. plz help me!!!

1)if  a/4 = b/5 = c/9  then  a+b+c/ c is  a)4  b)2  c)7  d)none of these

2)if a/4 = b/5  then  a )a+4 / a-4 = b-5 / b+5  b)a+4 /a-4 =b+5 / b-5  c) a-4 / a+4 = b+5 / b-5 d) none of these

3) if a:b = 4:1 then sq.rt of a/b + sq.rt of b/a is  a) 5/2  b)4 c)5 d)none of these

4) if x / b+c-a = y / c+a-b =z / a+b-c then (b-c)x + (c-a)y + (a-b)z is a)1 b) 0 c)5 d) none of thse