I've managed to figure this out by looking at similar posts (Sorry... I did say I was new!)

Anyway, here are the steps to transpose t = P*R/S*E-0.6*P making P the subject:

1. Multiply by (SE-0.6P)

2. Expand t(SE-0.6P)

3. Add +0.6Pt

4. Factorise PR+0.6Pt

5. Divide by R+0.6t

6. Rearrange P to L.H.S

If I've got this wrong, could someone let me know?