90дм 4мм-8м 34см=

To solve this expression, we need to convert all the measurements to the same unit. It can be either decimeters (dm), meters (m), centimeters (cm), or millimeters (mm). We will do the calculation in centimeters here because it is easier to work with whole numbers.

First, let's convert each term into centimeters:

1dm = 10cm, so 90dm = 900cm 1mm = 0.1cm, so 4mm = 0.4cm 1m = 100cm, so 8m = 800cm 34cm remains the same as 34cm

Now let's rewrite the expression in centimeters:

900cm + 0.4cm - 800cm - 34cm

Next, we combine the like terms:

(900 + 0.4) - (800 + 34) = 900.4cm - 834cm 900.4cm - 834cm = 66.4cm

Now, to return to a combination of units, we'll convert centimeters back to meters and centimeters:

Since there are 100 centimeters in a meter, 66.4cm is equal to 0 meters and 66.4 centimeters:

66.4cm = 0m 66cm 4mm

So, the result is:

90dm 4mm - 8m 34cm = 0m 66cm 4mm

If you need the result in a different unit or a simplified form, please let me know, and I can provide the conversion.