First, when the clock shows 4 o'clock, the difference between the hour hand and the minute hand is 20 squares, which can be regarded as a catch-up problem. The minute hand moves every minute 1 grid, and the hour hand moves every minute 1 grid. If the minute hand wants to form a non-overlapping straight line with the hour hand, it must not only catch up with the original difference of 20 squares, but also catch up with the other 30 squares. So the speed difference of pursuit is 1 1. Then divide 50 by 1 1, and the answer is 54 and 1 1.

30 times

1039? 37- 16=3×7 85-37= 16×3 196-85=37×3 ...

6:9=2:3

6×3/﹙2+3﹚×5= 18

18+ 18=36

:[80- 12×(80-20)÷ 18]÷( 1-80%),

=[80- 12×60÷ 18]÷0.2,

=[80-720÷ 18]÷0.2,

=[80-40]÷0.2,

=40÷0.2,

=200 yuan.