Answer:
add 6 unit tiles
Step-by-step explanation:
The square is completed when the algebra tile grid pattern is a square. This one will be a square when 6 more unit tiles are added to fill the empty spaces at the bottom right.
The answer for -3/8 divided by -6/7 is 7/16
OM and OP will coincide a second time after 120 seconds. You could visualize it as ray OP moving at 3 degrees/second relative to OM.
Using this visualization, we find that OM makes 30*60*3/360 rotations (minutes * 60 * rotational speed/360 degrees in a rotation), which is 15, and that OP makes 30*60*6/360 or 30 rotations, which is 15 more than OM.