Step-by-step explanation: U must first link the like terms so in order to do so u must bring over the 7m, now before u brought over the 7m it was a positive 7m now that your bring it over it turns negeitive and the same goes for the term 8n when u carry that term over it turns positive now dont let the subtraction sign foul u it still negative as long as its beside the term it is going to be negative guys dont forget that, now on to the next step after u cross over and change signs u start to work out now that the like terms are equal u dont need to worry about them because its given u the go ahead to workout so your main focus is on the subtracting the 7's which is 0 and leaves u with m u dont have to put them but i dont recommend it the u start on the next side u and the 8's which is 16 and u put bk the n u have to put bk the terms its important and thats how u get m=16n.