1a) L is directly proportional to Y therefore L=kY where k is a constant
X= L+9 therefore L = X-9 -> substitute in values of X to find L,
Therefore L= 24 - 9= 15
We are given that y= 5
And we know L= Ky
Therefore 15= 5k -> K=3
So relationship betwen L and Y -> L= 3y
1b) To find what y is when L is 12 simply sub in 12 and solve the equation
therefore 12 =3y
Y= 12/3 = 4
Note: Do you reckon you could take a wider picture? There seems to be some missing info from that question, so can't really begin to answer it without it.