600/x=450/(x-50)

The solution is x=200.

9) Solution: Set the harvester to harvest X hectares of wheat per hour.

10/x+ 1 = 10/( 1/ 150 * x * 100)

Solution: x=5

10) solution: let the driving speed of the previous hour be x km/h.

( 180-x)/x-2/3 =( 180-x)/( 1.5x)

Solution: x=60

1 1) because S=π(R squared -r squared) +2*a(R-r)

So a=S-π(R squared -r squared) /2(R-r)

12) 1) No, because after sharing = (Party A+Party B+Party C) /abc

According to the implicit condition of denominator, a, b and c are not 0, then the square of a+the square of b+the square of c is not 0, so the result is not 0.

2) Same as 1), and cannot.