Curtis has done it right because Tara forgot to put (10) and accidentally put (1) and that's where she lost herself. It wet downhill from there.
Constant is the scale term in proportionality. Suppose one variable is dependent on the other and one variable become twice, other becomes also twice and if one becomes half, other too becomes half., but they are two different variables which are no-where linked (like cost(money) vs quantity). Quantity and cost are two different things but they abridge a mathematical relation of proportionality. So in the mathematics to abridge these two different variables, we need something. Constant serves that purpose.
The 2 possible ways to fence in the patio are having 8x9, with the nine being the length of the wall. Because 8+8+9=26. The second way is 18x4 and the 18 being the length of the wall. Because 18+4+4=26.
Um i would need more details
But i thing you would add those together