1 Solution: Assume that X people are needed to process the shaft and Y people are needed to process the bearing.

X+Y= 180。

15X= 12Y

X=80，Y= 100。

Answer: It takes 80 people to process the shaft and 100 people to process the bearing.

2 Solution: We buy 65438+X in 0 yuan and Y in 0.5 yuan.

Then X+0.5Y=30 and X+Y=40.

X=20，Y=20。

A: 20 pieces of each.

3 solution: let a number be x and b number be y.

Then 2X+3Y=25 and X/2-Y/3=3.

2X-4Y/3= 12

The solution is X=8 and Y=3.

A: The number A is 8 and the number B is 3.

Solution 4: Suppose there are X male athletes and Y female athletes.

Then X+ 1=Y, 1500X+800Y= 10000.

The solution is X=4 and Y=5.

A: There are four male athletes and five female athletes.

Second, because |x-3y|≥0, |2x-y-5|≥0.

And |x-3y|+|2x-y-5|=0.

So x-3y=0, 2x-y-5=0.

X=3，y= 1。

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