Bran's scholarship pays $90 x 0.30 = $<<90*0.30=27>>27 to his tuition fee.
So, the total amount he still needs to pay is $90 - $27 = $<<90-27=63>>63.
And Bran will be able to earn $15 x 3 = $<<15*3=45>>45 after working for 3 months.
Therefore, the total amount he still needs to pay is $63 - $45 = $<<63-45=18>>18.
#### 18