(2x – 4) + (7x + j) = 9x – 12

find j please!!

Me answer number 3plz explain how you do it

100 points and 1- -12=y-36 2- x/25=-25 3- -n=40

The snowstorm lasted a total of 9hours it snowed at a rate of 1 inch per hour during the first 2 hours the snow continued for the next 6 hours falling at a rate of 2 inches per hour,and finally reduced to 1 inch per hour for the last hour