2000+0.02x= 1600+0.04x

X equals 20000.

When the sales volume is less than 20000, choose a.

When the sales amount is more than 20000, choose B.

If you want to use inequality, convert it (change = to less than or greater than)

Let x be the image.

Image of:

When x= 10000 and y (salary) =2000+200=2200, the coordinates (10000,2200) are obtained.

When x= 15000 and y=2000+300=2300, the coordinates (15000,2300) are obtained.

Draw a picture on the coordinate system according to two coordinates.

Image of b:

When x= 10000 and y (salary) = 1600+400=2000, the coordinates (20000,2000) are obtained.

When x= 15000 and y= 1600+600=2200, the coordinates (15000,2200) are obtained.

Draw a picture on the coordinate system according to two coordinates.

The coordinates of the intersection of two straight lines should be (20000,2400).

therefore

When the sales volume is less than 20000, choose a.

When the sales amount is more than 20000, choose B.