by JasonLion » Thu Nov 20, 2014 2:50 am
To be a little more verbose, consider where in row 3 you can put a seven. There are only three open cells in row 3, and two of them have a 7 in their column. That means the remaining cell must contain a 7. Thus, the first move daj95376 suggested: R3C5=7. This kind of logic is called a hidden single.