Need help badly with changing the subject of a formula (maths)?

Like ping the parcel, unwrap the layers to isolate the term containing the letter you want; In qu 1)x/t = u + v/2 -> x/t - u = v/t then multiply by t; x - ut = v but qu2) is a quadratic so make = zero then multiply by 2; at^2 + 2 ut - 2x =0 and your solutions come from the quadratic formula where a X^2 +bX +c =0 here a=a, b=2u and c = -2x . I'm sure you know the rest! qu3) like qu1); u^2 = v^2 - 2ax then square root both sides. qu4) multiply out right hand side m1(v1-u1) + m2v2= m2u2 now divide both sides by m2; u2= m1(v1-u1)/m2 + (v2). qu5) similar to qu4). qu6) (W/Fx) =cosy then inverse; y = cos^(-1).(W/Fx). qu7) Invert both sides and divide by 2m; 1/(2mW) =v^2 -u^2 so v^2 = u^2 + 1/(2mW) then Square root both sides. qu8) Invert both then multiply by n2. qu9) sini = n2 sinr / n1 then inverse; i = sin^-1 [n2.sinr / n1]