You are coming up with the strangest questions!
Do it in bits.
1. 4x <= 15
x <= 3 3/4
2. 15 <= –9x
–9x => 15 (just swap the sides around)
x <= –1 2/3 (remember to change the direction of the inequation when dividing by a negative)
Now both these conditions have to hold simultaneously. So the overall solution must be x <= -1 2/3.
x=0 is not a valid solution, as it doesn't satisfy the right part of the equation.