Henry and his dad are building a new fence around their square chicken coop. Each side of the chicken coop is 2j + 7 feet long.
How many feet of fencing is needed if j= 12 ?
__________ feet
If the length of each side of the chicken coop is 2j + 7 feet, then substituting j=12 into the equation yields 2(12) + 7 = 24 + 7 = <<2*12+7=31>>31 feet per side.
Since there are four sides to the square chicken coop, the total length of fencing needed is 31 feet/side * 4 sides = <<31*4=124>>124 feet.
Therefore, 124 feet of fencing is needed. Answer: \boxed{124}.