1, 200*35%=70 pieces

2、200*25%*80%+200*40%*85%+200*35%*90%/200 * 100%=85.5%

3. Set the energy.

Then the excellent product rate is 85.5%+3%=88.5%.

Then the quantity of excellent products is: 200*88.5%= 177 pieces.

We buy X pieces from A, Y pieces from B and Z pieces from C.

X+y+z = 200 ......................................1formula.

X * 80%+Y * 85%+Z * 90% = 177 ……

1 equals the sign left and right times 0.9:

0.9x+0.9y+0.9z = 180 ……

Type 3 -2:

0. 1x+0.05y = 3

note:

X, y and z should all be integers.

therefore

When x=0 y=60 z= 140.

When x= 1 y=58 z= 139.

When x=2 y=56 z= 138

…………

When x=30 y=0 z= 170.

You can abbreviate it here, but I wrote it this way to make it clearer.

Therefore, Happy Company can meet the condition of 3% improvement in the rate of excellent products by purchasing no more than 30 A products in a factory.