Solve:

21/8.1 = 105/m

Cross-multiplying, we get:

21m = 8.1 x 105

Simplifying the right-hand side, we have:

21m = 850.5

Dividing both sides by 21, we get:

m = 40.5

Therefore, the solution is m = 40.5.

To solve the equation (21/8.1) = (105/m), we can cross-multiply.

Multiply 21 by m and 8.1 by 105:
21m = 8.1 * 105

Now divide both sides of the equation by 21 to solve for m:
m = (8.1 * 105) / 21

Perform the multiplication:
m = 850.5 / 21

Finally, divide 850.5 by 21:
m ≈ 40.5

Therefore, the solution to the equation is m ≈ 40.5.