The remainder of an angle is half of the complement of the angle, 42 degrees less There are some 4% salt water, which evaporates some water and turns into 10% salt water. Then 300 g of 4% salt water is added to mix or turn into 6.4% salt water. Ask about the quality of salt water initially added Find the time between 5 o'clock and 6 o'clock when the hour hand and minute hand are in a straight line For a five digit number, if the number in the first digit is moved to the last digit, a new five digit number can be obtained (for example, this transformation can get 3214 from 4321), the new five digit number is 11106 smaller than the original number, and the original five digit number can be obtained Set up the unknown number and list the equation

The remainder of an angle is half of the complement of the angle, 42 degrees less There are some 4% salt water, which evaporates some water and turns into 10% salt water. Then 300 g of 4% salt water is added to mix or turn into 6.4% salt water. Ask about the quality of salt water initially added Find the time between 5 o'clock and 6 o'clock when the hour hand and minute hand are in a straight line For a five digit number, if the number in the first digit is moved to the last digit, a new five digit number can be obtained (for example, this transformation can get 3214 from 4321), the new five digit number is 11106 smaller than the original number, and the original five digit number can be obtained Set up the unknown number and list the equation

1 (180-x)/2-42=90-x
x=84°
2 (x*4%+300*4%)/（x*4%/10%+300）=6.4%
x=500
3 if y is set, then Y / 60 * 360-y / 60 * (1 / 12) * 360-5 * (1 / 12) * 360 = 180
Y = 60, at six o'clock
The fourth question will take some time. I haven't thought of it yet