by using bi linear interpolation

Let suppose your rollno's first two digites are the X and last 2 digits are Y.i.e if your rollno is 200092 then X=20 and Y=92 . and Q11=120, Q12=90 , Q21= 135 AND Q22=150 find the value of P(X,Y) by using bi-linear interpolation.

[John D'Errico]

Far too confusingly stated to get any answer that will make any more sense than your question.

Break down any problem that is too complicated to solve for you into simple sub-problems. Solve each one in turn.

Here, that first means figuring out how to extract X and Y from rollno.

Next, you need to learn how to perform bilinear interpolation, since It seems clear you don't understand that. Or learn to use interp2. Or perhaps you really don't want to use bilinear interpolation, you just think you do. We don't know what is the real issue here.