You can start by setting up the equations that are given in the stem of the problem: a=.5b, c=b-50, a+b+c=180. Then plug in the values of b in relation to the other values into the equation a+b+c=180. This will give you (.5b)+b+(b-50)=180. By expanding this and combining like terms, we will get 2.5b=230. By dividing each side by 2.5, we get b=92. Then, referencing the first equations, a=.5(92)=46, and c=92-50=42. The smallest of all of these is c, 42.