1. 20/20 VISION
Use the digits 1 through 9, in increasing order, to make the new year of 2020. You can only add the symbols + – × / ( ).
3. TWO-DIGIT TOPOLOGY
Insert a different two-digit number in each circle. Circles are connected by a line if the numbers they contain either differ by 1, have a ratio of 2 or 3, or look like the other when turned upside down. For example, 92 could be connected to 26, 46, 91, or 93. Leading zeroes are not allowed.
4. MNO
In every grid below, each row and column should contain 2 dots and 1 letter. The letter M indicates it is the Midpoint of the dots in its row and column. The letter N indicates it is between the dots but Not the midpoint. The letter O indicates it is Outside the dots. Fill in the missing symbols and dots.
5. CHESS MATES
Add a white piece to the position below so that there is mate in 1 move. Then add different white pieces to the same square so that there are mates in 2, 3, and 4 moves. (Thanks to George Sicherman)