think of the = sign as a balance beam, every time you move a number across it the sign will change (ex: 1x+3=6-2 if u move the 3 across to have just the x variable you will have 1x=6-2-3 or 1x=6-5) so nx-r=p would be nx=p+r if u are solving for x you want to divide by the number attached to x which is n you do x/n=p+r/n. and since there are no numbers you cannot solve any further