.) TRAnsitive; think like aTRAin. the cars are connected...
N is connected to X and X is connected to C, so N is connected to C
2)reflexive; think refection, like a mirror,
3)substitution; substituted 40 for mB
4)division prop of eq; both sides of equation divided by 4
5)AB = 25 - CD; subtracted CD from both sides
