Let's evaluate each expression step by step.
**Question 1: Evaluate the expression \(6a + 4b - 3c\) for \(a=3\), \(b=5\), and \(c=10\).**
Substituting the values into the expression:
\[
6(3) + 4(5) - 3(10)
\]
Calculating each term:
\[
6 \cdot 3 = 18
\]
\[
4 \cdot 5 = 20
\]
\[
3 \cdot 10 = 30
\]
Now combine the results:
\[
18 + 20 - 30 = 38 - 30 = 8
\]
So, the answer for Question 1 is:
\[
\boxed{8}
\]
---
**Question 2: Evaluate the expression \(2.4x + 6.2y\) for \(x=3.5\) and \(y=1.8\).**
Substituting the values into the expression:
\[
2.4(3.5) + 6.2(1.8)
\]
Calculating each term:
\[
2.4 \cdot 3.5 = 8.4
\]
\[
6.2 \cdot 1.8 = 11.16
\]
Now combine the results:
\[
8.4 + 11.16 = 19.56
\]
So, the answer for Question 2 is:
\[
\boxed{19.56}
\]