Answer:
your going to cross multiply on all of these and then solve them normally
11.) z to 4 = 8/5
z x 5 = 4 x 8
5z = 32
z = 32/5
12.) 9 to 15 = 15 : y
9 x y = 15 x 15
9y = 225
9y/9 = 225/9
y =25
13.) 11 : x = 5 to 1
11 x 1 = 5x
11/5 = x
~batmans wife dun dun dun....
