To solve the first expression:

7(4-3x) - (8,5-x) = 4 - 3(x-8)

First, we will distribute the 7 and simplify:

28 - 21x - 8.5 + x = 4 - 3x + 24

Combine like terms:

-20x + 19.5 = 28 - 3x

Now, move all the x terms to one side of the equation:

-20x + 3x = 28 - 19.5

-17x = 8.5

Now divide by -17 to solve for x:

x = -0.5

To solve the second expression:

3(0.5m+0.7n) - 5(0.3m-0.4n)

First, distribute the 3 and 5:

1.5m + 2.1n - 1.5m + 2n

Now combine like terms:

2.1n + 2n = 4.1n

Therefore, the simplified answer is 4.1n