Solve for n
s+nq squared t= -4q

Hope you think it in this way wrote 

S+NQ^2 *T = -4Q solve it for N    so subtract from both sides an S and will get 

S-S +NQ^2 *T = -4Q -S

NQ^2 *T = -4Q -S   divide both sides by T and will get 

NQ^2 = (-4Q -S)/T    divide both sides by Q^2

N = (-4Q -S)/(Q^2 *T)

hope helped